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THE

ANEROID BAROMETER:

ITS

CohrsTRiicrror\ Ar\D llsE,

EIGETE EDITION"

REVISED AND ENLARGED,

NEW YORK:D. VAN NOSTRAND COI\{PANY,

23 MunnAy AliD 22 WennnN Srnnnr.1902.

'o g3q '.o f.rg

.oBflrfT .

",Fi$r.

CONTENTS.

PAGE.

Cur,ptnn I.-Thg Atmosphere...............r 5

t-'sr.ernn ll.-Barometric Measurements

of Altitud.es... ...... .....r..'........ 27

Cslprnn Ill.-Aneroid Barometers ; Their

Construction............ ......... r..... ......... 39

C'slrrEn IY.-The IJse of Aneroid Bar-

ometers..............o.........s.....e .....r 52

{.xrrrnn Y.-Suggestions in Regard tothe Selection and Systematic Use of

- aq Aneroid... ......'.. .-.., .................o...,

TrBr,n l.-Prof . Airy's Table of Altitudes.Tsr,n II. -Logarithmic

Tablo.. . . o.. .. . ... . . .

Trnr,n IIL-Metric Altitude Table. ...... o..

Tsl,p IY. -Corrections

for Mercurial Bar-

Omgtgr. . ........................ ....o..'..........

Trnr,B \'.-Boiling Point of Vlater cor-

responding to Different Barometrie

7rr

88

106

tzt

135

PrgSSUfeS. . .. r .....t. t... t ...'...i. . t...... r cr . . o. ]. 36

PREFACE TO SECON D EDITION.

Tun fact that the firstlittle manual is entirely

suffi.cient indication thatwant. As the use of the

edition of thisexhausted is ait supplied ai

Aneroid Bar-

ometer is on the increase, the presump-

tion is that there will be a, furtherclemand for this book of tables an,i[ in-

structions.

It has been thought ad,visable to re-

ar'I'arlg:e the matter and to increase itbr fuller d escriptions of different in-

struments ; and. what is of more im-

portance to the noviee in measuring

aititucles, to add a number of ex-

ampies. '1r

Another table has also been added to

the collection of the previous edition.

TH E AN EROID BAROM ETER :

ITS CONSTRTICTION AND USE

CHAPTER I.

rhe *;H. :;I,il;;lo'*o,,ound s

our globe, and to which we give the

name of atmosphere, is subject to many

and varied changes. In the relativeamount of the two gases which chiefly

compose it, it remains marvelously coII-

staqt; yielding upon analysis the same

ratib of oxygen to nitrogen for all lati'tud.es and all altitudes. ft i* only withina, few restricted and generally confi-ned

areas where the natural chemical Pro-cesses of respiration, combustion or fer-mentation are active, that the free'oxy-gen is found to be notably deficient, and

the product, carbonic dioxide, which ex'ists normally to the ertent of one twen'

6

ty-fifth of one per cent', is, to a' corre-

spond"ing extent, in excess'

\Yhenl ho*.ver, we regard' the condi-

tions which arise from its physical prop-

erties, no such constancy is observable.

Indeed, it seems the most fitting type of

a transibcry state, and whether we regard.

the teruperature, the moisture, the lless-111.e resulting from its weightr of the di-

rection ancl velocity of its motions, we

can only accluaint ourselves with the

limits within which these conditions have

been known to vary. The nature of

the changes within these limits we can-

not, in the present state of our knowl-

edge, assume to predict for the future,

except for very limited periocls; and. even

then the prediction is set forth only as a,

" probabilitY.'certain average conditions are noticea-

ble as belongiog to certain areas or zones

of the earth, and differing somewhat

among themselves, especially ''' as togreater or less range in temperature,

moisture, etc. To such general condi-

I

II

Il

II

I

II

I

{II

I

itI

i

i

1

;

1

iii

I

tions we aPPIY the term cli'mate'

,(

The department of science which re-gards the physical phenomena arisingfrom these varying cond.itions is caIledmeteorology. The instruments emplovedwith which to indicate or measrlre theextent of tirese changes, are of variouskinds. Thus the thermometer indicatestlre relative temperature, the hygrometerthe humidity, the a?Leruonr,eter the forceor the velocity of the rvind, and the bar-ometer the pressure of the afu whicharises clirectly from its weight.

It is with the last of these instrumentsthat we are especially coneerned in thepresent essay. ft has two quite distinctuses : One to indi cate the varying press-ures of the air at some fixed point formeteorological purposes, and. the otherto indicate difference in altitude of pointsto which the instrument is carried by af-fording a measure of the greater or lessamount of atnaosphere above it. Beforeusing the instrument to measure alti-tudes it is important to become some-what fanriliar with its use as a stationaryinstrumont. The barometer most fre"

1i. ,}.,i,{

8

quently employed for such use is the oneinvented by Toricelli in 1643. It is toowell known to req'uire description here.It will be suffi.cient to say that it meas-ures the varying pressure of the air bythe varying length of a, column of mer-cury which l'ralances the pressure.

When the barometer is employed forthe purposes of meteorology only, thefollowing facts are taken into considera-tion. We quote from Buchan's " HandyBook of Meteorology."

Yari,ations of the Baromsf,sv.-Thevariations observed. in the pressure ofthe air may be tlivided. into two classes,

viz., periodical and irregular ; the peri-odical variations recurring at regular in-tervals, whilst the irregular variations,observe no stated times. The mostmarked of the periodical variation is thedai,l,y uariat'iott,, the regularity of whichin the tropics is so great that, aceordirgto l{umboldt, the hour may be"* ascer-

tained from the height of the barometerwithout an error of more than L5 or LT

minutes on the average. This horary

til

Ij

a

oscillation of the barometer is masked inGreat Britain by the frequent fluctuationsto which the atmosphere is .subjectecl inthese regions. rt is, howeyer, detectedby takirg the mean of a series of hourlyobservations conducted for some time.The results show two maxima occurringfrom 9 to 11 A.M. and from g to L1 p.M;a,d. two minima occurring from B to 5a.M. and from B to E p.M. (See Tab1e,page 10.)

The maxima occur when the tempera-ture is about the mean of the duy, andthe minima when it is at the highest andlowest respectively.

This daily fluctuation of the barometeris caused by the changes which takeplace from hour to hour of the duy inthe temperature, and by the varyingquantity of vapor in the atmosphere.

fhe surface of the globe is alwaysdivided into a day and night hemisphere,separated by u great circle which revolveswith the sun from east to west in twenty_four hours. These two hemispheres ur.thus in direct contrast to each other in

IU

6.c,cocgoorceoGtiarml-6C)6)OJGQ6?-<=J6O-{-OOOO-

.^ rO OO rr O 0O'+l 6! O q2

*eqqsqqqqsE+++++++++

EtEEESqHEeElllllllllil;6OCQTOC\bmqgQ

;--qqqq-qqE+++++++++

uieoanart-,rr'-@o\@c)16a66r?t--riOir-rOO=6OOOOOOOO,.E t' t' t' l' t' t' l' t' l'

zizzizz@ cgfrer{Fl@??*ete\*e

OO@G\TGQOJTOOOJ-- rt C\ 60 -+l Io l()

Xt3A

z=tA

X\Ja

zHtJa

d{P

odr)

gFl

q)Ho0)ri

68F{t-tq)

a

tr6q)()oOqC)cB

AFI

Hq€q)CJ

ocJ

{J

tr6+"

doztr

zH

frtr]Ertrll={aofr

Fq

trl

Hr-.

f-l

zrrA fr]FtA

Ha)ztia.-!zH9HHzHrn,-{ Ft- tr{

F'{ RFlH

RtrlFIH

ozHFol+{

atr]flFq

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il

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respect of heat ancl eyaporation. Theirernisphere exposecl to the srln is warm,ancl that turnecl in the other clirection iscold. Owing to the short time in whicheach revolution takes plaee, the time ofgreatest heat is not at noon, rvhen the sunis in the meridian, but about two or threelrours thereafter; similarly, the period ofgreatest cold occurs about four in themorning. As the hemisphere under thesr1rl's rays becomes heated, the air, ex-panding upwards and outwards, flowsoyer upon the other hemisphere wherethe air is cold.er and. denser. There thusrevolves round the globe from duy to day,a wave of heat, from the crest of whichair constantly tends to flow toward.s themeridian of greatest cold on the oppositeside of the globe.

The barometer is influenced to a largeextent by the elastic force of the vaporof water invisibly suspended in the at-mosphere, in the s&me way as it isinflu-enced by the dry air (oxygen and. hydro-gen). But the Yapor of water alsoexerts a, pressure on the barometer in

L2

another way, Yapor tends to diffuseitself equally through the air ; but as theparticles of air offer an obstruction to thewatery particles, about 9 or 10 A.M.r whe.s

evaporation is most rapid., the vapor il;accumulated. or pent up in the lowerstratum of the atmosphere, and beingimpe,iled in its ascent its elastic force isinereased. by the reaction, and the barom-eter consequently rises. -When the airfalts below the temperature of the dew-

point, part of its moisture is depositedin dew, and. since some time must elapse

before the vapor of the upper strata can

diffuse itself downwards to supply thedeficiency, the barometer falls-mostmarkedly at 10 p.M., when the depositionof dew is greatest.

Hence, &s regards temPerature, the

barometer is subject to a maximum andminimum pressure each day-the maxi-mum occurring at the period" of greatestcold, and the minimum at the period ofgreatest heat. And as regards Yapor inbhe atmosphere, the barometer is subject

o two maxima and minima of pressure-

13

ohe maxima occurring at 10 A.M., lvhen,owing to the rapi,fl evaporation, the accu-mulation of vapor near the surface isgreatest, and, about sunsetr or just be_fore dew begins to be deposited., whenthe relative amount of oupo, is great ;arrd. the minima in the evening, when thedeposition of dew is greatest, and beforesunrise, when evaporation and the quan-tity of vapor in the air is least.

Thus the maximum in the forenoon isbrought about by the rapid evaporationarising from the dryness of the air andthe inereasiog temperature. But as theva,por bee.omes more equally diffused,and the air more saturated, evaporationproceeds more languidly ; the air Lecomesalso more expancled by the heat, andflows away to meet the tr.iurnar wave ofcold advanciog from the eastwards.Thus the pressure falls to the afternoonminimum about 4 p.M. From this timethe temperature declines, the air.,ap-proaches more nearly the point of satu-ration, and the pr..*rre being f*rtherincreased by accessions of air iro* the

', :;1{iwlryi',?.li::'

L4

\Yarm wave, now considerablY to the

westward., the evening maximum is aL-

tained. As the deposition of dew pro-

ceeds, the air becomes drier, the elastic

pressure of the vapor is greatly dimin-

ished", and. the pressure falls to a second

minimum about 4 e'-rvr.

The amount of these daily variationsdiminishes from the equator towards

either pole, for the obvious re&son thatthey depend, directly, or ind-irectIy, olr

the heati:rg power of the sun's rays'

Thur, while at the equator the daily fluc-

tuation is AJ25 inch, in Great Britain itis only a sixth part of that amount- Itis very small in the high latitudes of St-

Petersburg and. Bossekop; and in stillhigher latitudes, r,:t' that period of theyear when there is no alternation of duy

ancl night, the d.iurnal variation probablydoes not occur. In the dry climate of

Barnaul, in Siberia, there is no evening

maximum ; the lowest minimum occurs

as early as midnight, and the only maxi-

mum at 9 A. Iu.

Since the whole column of the at-

1t)

mosphere, fronr the sea-level upwards,expands during the heat of the .luy, thuslifting a portion of it above alr praces aLhigher levels, it is evident that in" after-noon minimrlm at high statio,.s wilt beless than at lower stations, especiarywhen the ascent from the one to the oth--er is abrupt. Thus, at paclua, in ftaly,the afternoon minimurn is 0.014 inch, t utat Great st. Bernarcl it is only ti.oogineh.

Annual Yuroatdon.-When it rs sum-mer in the one hemisphere, it is winterin the other. In the hernispher.e wheresummer prevails, the whole air beingwarmer than in the other hemisphere,expands both vertically ancl laterally. A;a, consequence of the lateral expansionthere foll,ws & transference of part ofthe air from the r,varrn to the cold hemi-sphere along the earth's surface; and, asa consequence of the vertical expansion,an overflow in the upper regions of the at-mosphere in the same direction. r{ence,i, so far as the dry air of the atmosphereis concerned, the atmospheric pressure

:ji?wm*i

tr6

will be least in the summer and greatestin the winter of each hemisphere. Butthe production of aqueous Ya,por by evap-

oration being most active in summer, thepressure on the barometer will be muchincreased from this ca,use. As the aque-

ous vapor is transferred. to the colderhemisphere it will be there condensed

in',o rain, and. being thereby withdrawnfrom the atmosphere, the barometerpressure will be diminished; but the dryair which the yapor brought with it fromthe w&rm hemisphere rvill remain, thustending to increase the pressure.

In the neighborhood of the equator

there is little variation in the mean press-

ure from month to month. Thus, atCayenne, the pressure in January is29.903 inches, and in July 29.957

inchesAt Calcutta,22o 36' N. lat., the press-

ure is 29.408 in July, and 30.102 in Jan-uary, thus showing a difference of 'O.694

and at Rio de Janeiro,22" 57' S. lat., itis 29.7L+in January (sumrner), and 29.978

in July (winter), the difference being

lt

\.

t7

0-234. The large annuar variation atcalcutta is caused jointly by the greatheat in July, and by the Luroy rainswhich accompany the south-west mon-soons at this season; whil" in Januarythe barometer is high, owing to thenorth-east rnonsoons, by which the drycold dense air of central Asia is con-veyed southward over India.

At places where the amount of vapor inthe air varies little from month to month,but the variations of temperature aregreat, the difference between the summerand winter pres"sures are very striking.T}us, aL Barnaul and frkutsk, both i"siberia, the pressures in Juty are respect-ively 29.243 and 2B.zG7, and in January29.897 and 28.86b, the ,ilifferences beingupwards of six-tenths of an inch. Thegreat heat of siberia during summercauses the air to expand and flow awayin all directions, and the diminishedpressure is not compensated for by"anymaterial accessions being mad.e to thea,queous vapor of the atmosphere; and,on the other hand, the great cold and,

II

l--t

18

little rain in that region during wintercauses high pressures to prevail during

that season. The same peculiarity is

seen, though in a, motlified degree, al

Moscow, St. Petersburg, and' Yienna'

At Reykjavik, in lceland, the pressure

in Jtrne is 29.7LT, and in December

29.273; trt Sanchvieh. Orkney, 29'775,

ancl 29.586 : &nr[ at sitcha, in Russian

Arnerica, 29.975. ancl 29.664' In all

these pla,ees the clistributiou of the press-

ure is just the l.eyerse of rvhat obtains in

siberia, being least in rvinter and great-

est in summer. The high summer press-

Llres are due to the cooi Summer tem-

peratures as comparecl with surrounding

countries, thus causing an i'n'florn fromthese regions, and. to the large amount of

vapol. in the a,tmosphere, thus still fur-

ther raising the barometric column. on

the other hand, the low winter pressures

are due to the comparatively high winter

temperatures eausing an ouffiow tgu:ards

u,djoi,ning countr'ies, atd, the large winter

rainfall which, by setting free great quan-

19

tities of latent heat, stilt further aug.-ments and aecelerates the outflow.

The variations in rnean pressure arevery slight, and not markecl by any yer,rrdecided regularity in ilreir march thro"gilthe seasons, at Dublin, Glasgow, London,Paris, and Rome. As compared withBarnaul and Reykjavik their temperatureis at no season very different from thatof surroundi,g eountries, and the vaporand ,ainfall are at no time much in excessor defect, but are more equally distributed o..er the different months of theyear.

At the Great St. I3ernard, gt71 feetabove the seA, the llressure in summer is22.364 inches, whiie in rvinter it is only22 A4,4. At Padua, there is sear.cely anydifference in the pressure between sum-mer ancl winter. The i,r,rease in thesummer pressllre at the Great St. Ber-nard is no doubt due to the same causealready referred to in art. 6b-vi 2., .theexpansion of the air upward cluring thewarm summer months, thus raising qlarger portion of it above the barometer

.i:.,rlrl'f mmmmmffi EBf L,:-',.'-

ffirP'i"

20

at the highest station. But at St. Fe deBogota, 8615 feet high, nea,r the equator,and where, consequently. the differencebetween the temperature in July and.January is very small, the difference iuthe pressures of the same months is alsovery small, being only 0.035.

Distri,butzon of Atmosptheric Press-ure ouer the globe, as cletermi,rted by theAnnual -Iltfeans.-Though much addi-tional observation is required, especiallyin A frica, Asia, and South America, be-fore the isobarometric lines can be laidclown on e"map of the world, yet manyimportant conclusions regardirg themean barometric pressure have been ar-rived at from the results already obtained.We have seen that the daily an.l mouthlyvariations of pressure observed at differ-ent places are modified by the variationsof the temperature of the air, the amountof vapor, and. the rainfall. Since theseare in their turn greatly modifiecl by.*theunequal distribution of land and wateron the earth's surfaeer we should. expectto fincl the pressure, and the variations

I

2L

in the pressure, most regular in thesouthernhemisphere. Accol..lingly, thereis a' remarkabre regurarity observed inthe distributio, of ilre 1rru...rru fromabout 40" I{. lat.'southword. to the Ant-arctic oeean, rvith the exception of theregion of the rnonsoorls in southern Asia.

The mean pressure in the equatoriutregions is about 29.90 ; at 20" N. lat. itrises to 30.00, ancr at Bs' I{. rat. to 80.20,from which northwards the pressure isdiminished. The same pecuriarity is seensouth of the equator, but it is not sostrongly marked. At 45" S. Iat. it fallsto 29.90, and from this southward.s iteontinrles steadily and rapidly to fail to amean pressure of 29.91 at 7 5" s. lat.This extraordinary depression of thebarometer in the Antartic oeean, beingone inch less than at the equator andL,326 inches less than at Atgiers, is per_haps the most remarkable fact in themeteorology of the globe. *.

Th" pressure in the north temperateaad frigid zones is in striking contrast tothe above. From Athens,

-in a north-

-

22

eastern direction, a high isobarometricline traverses Asia, passing in its course

Tiflis, Barnaul, Irkutsk, and- Yakutsk.

To the east of the northern part of thisare& of high mean pressure, around the

peninsula of Kamtschatka, there is a,

region of low barometer, the mean press-

ure being only 29.682. There is another

remarkable are& of low pressure around

Iceland, the center being probably in the

south-west of the islancl near Reykjavik,

where the me&n is 29.578. As observa-

tions are more numerous in Europe and

North Ameriea, the d,imensions of thisd.epression may be defined. with consider-

able precision by drawing the isobaro-

metric of 2i5.90, which is about the mean

atmospheric pressure- This line passes

through Barrow Straits in North Amer-

ica, thence south-eastward- toward- New-

foundland, then eastward through the

north of lrelan,il, the south of scotiand,and. the south of Swed-en, whence it pro-

ceeds in a, north-easterly d.irection to

Spitzbergen. " The followiog mean annual

Dressures will show the nature of the de-

I

23

pression : I{ew york, 80.001 ; paris,29.988; London, 2g.g56; Glasgow, 2g.g68;Orkney, 29.78L; Bergen, Zg.-SO+; Spitz_bergen, 29.794; Reykjavik, Zg.Elg; God_thaab, in S. Greenland, 29.605; Ilperna-vik, in N. Greenland, 2g.7gL; and MeI-nille rsland, 29.807. A depression alsooccurs in rndia, where the mean is oulyabout 29.850, whereas in the same lati-tudes elsewhere it is about 90.100.

There are thus four areas of row press-ure on the globe, the extent of each beingnearly proportioned to the depth of thecentral depression- -uiz., Antarctic ocean,the least pressure being 29.910 ; rceland,29.578; Kamtschatk a, 2g.6g2 ; and India,29.850 ; an,l three areas of high pressure,one lying between latitudes 20J and 40oN., another between l5o and. Bbo S., andthe thircl in central Asia, from south-west to north-east. These low meanpressures are by no means eonstant in allcases during the months of the year. .* fnthe Antartic ocean ilrey are nearly corr-stant during the months, with purhup* uslight tendency to an inereasu io winter.

24

In the region of low pressure around. Ice-land the pressure is a, little less thanelsewhere in summ€r; but in winter,when the rainfall is heaviest, it is verymuch less, being 0.251 inch less in winterthan in summer at Reykjavik, and 0.189

at Sand.wich, in Orkney. Similar1y at

Petropaulovski, in Kamtschatka, thepressure in winter is 0.323 less than insummer. I{ence the low mean annualpressures in the North Atlantic and the

North Pacific are chiefly brought aboutby the low pressure during the cold

months of the year, and are d.oubtless

caused by the copious rainfall durirg thatseason. On the other hand, in SoutheraAsia, the lowest pressures occur in sum-

mer. Thus, at Calcutta it is 29.408 inJrrly, while in January it is 30.102-theayerage pressure for that degree of northlatitud.e. Hence, i, Hindostan, the lowm.earr annual pressure arises from thevery low pressure in summer caused bythe heavy rains falling at that season,

particularly on the south slope of theEimalayas. Generally the pressure is

i

IIL

r

lri

I

I

III*fl

t

k

25

low wherever a copious rainfall prevailsorer a considerable portion of the earth'ssru'face, owing to the large quantity ofcaloric set free as the vapor is condensedinto rain.

It is scarcely necess ary to point outhow important it is to keep in mind thesefacts of the pressure of the atmosphere,it being evident, for instance, that a press-ure of 29.00 in the North Atlantic wouldportend stormy winds, while the samepressure south of Cape Horn, being themean pressure there, would irrdicate set-tled weather.

The readings of the mercurial barome-ter are subjected in nice observations toseveral corrections :

1st. To 32" F. allowance being madefor expansion of both mercuryand scale for at1 observationsabove that temperature. A baro-metric pressure of thirty inchesat 32" would be indicated by a,

height of 30rru inches at T0o. 52d,. For decrease of gravitation at sta-

tions above the level of the sea,

'rii#*rc'

26

acting on both the mercury andthe air.

3d. For increase of gravity with in-crease of latitude.

(Lh^. For temperature of air ; the den-sity ,ilecreasing as temperaturerises.

5th. For humidity of the air which. also influences its density.

6th. For capillary attraction of thetube.

F

27

CHAPTER II.BAROMETRIC MEASUREMENTS OT' AITITUDES.

Tnr text books in physics presentformulas for computing heights frombarometric observations, based on physi-cal laws which we will briefly give.

If the density of the air were constantthroughout, the mea,surement of heightswould be a problem of the simplestcharacter; for as mercury weighs 10,500times a,s much as air at the sea level, themercurial colunrn would faII one inch foreyery 101500 inches of aseent above thesea, But air is compressible, and., inaccordance with Boyle's law, its densityvaries with the pressure to which it issubjected.

Now suppose the atmosphere dividedinto layers of uniform thickness, but so

thin that the density may be considereduniform throughout.

28

Iret lr,:the thickness of each layer.W-weight of a cubic foot of air at

pressure I{.W,:weight of a cubic foot of air at H.

I{o H,, &c. -pressures Ineasured ininches of mercury.

Then the pressllre upon the unit ofsurfirce of any layer is greater than that'upon the surface of next higher layer, bythe x-eight of a volume of air whose base

is the unit of surface and whose heightis the thickness of the layer. If onefoot be the unit of surface, then thisquantity would be i,W. And to expressit by height of mercury column, it is

necessary to multiply by #which. aw30glves

2:157

But W: Wot : H: 30.'Wo being the weight of a cubic foot airat the level of the sea (-.0807 at 32"F).

IMe have from the above W X 3O,-IM.

X H, and the above expression for d.imi-

nution mey be written {YiY.2L57

IFF--

29

{ I{o I{, I{, represent the pressuresat the surfaees of the suecessive layers,we shall have

H,:rro-ff+-Hu(r- ffi)H,:r{,-ty#,:H,(r- ffi)Hu:H,-(r- ffi)I[,:Hn-r(r- ffi)

Multiplying these equations and sup_pressing coinmon factors, we get

H,:r,(r_ffi)"rt h be taken at one foot then za wourd.

represent the number of feet verticallybetween two stations at which the baro-metric pressures are Ho and I{o respect_ively.

By substituting for Wo its value andtaking logarithms we have

log E; -)t' log'\21b6. glgs)whenee

rL-60135.4Xlog. r{oH,

,iffi.,

'l

I

['

l

I

H

I

t

II

t

I

lI

#ilj

[$__

30

For use in accurate observations, cor-

rections are required for temperature,

humidity and variation in the force of

*'il*'*Iaee's formula which includ'es

terms derived from the consideration of

these conditions is obtained as fo110ws :.

Suppose a, portion of the atmosphere

inelu,iLed between two stations at differ-

ent altitudes to be divided into very thin]al.ninre.

Let z be the distance of one of these

from the surface of the globe and' dz itsthickness.

Let P be the Pressure upon a unit of

surface upon the lower side of this layer;

and 'W the weight per cubic meter of the

air at this pressure.Then the pressure on the upper side

will be less than P by an amount equal

to the weight of a column of air whose

base is a unit and height is equal Lo dz'

Whence x+

ctP - -W dz (1)

If Wo be the weight of a cubic meter of

air at the temperature OoC and. a baro-

31

metric pressure of fl.m 76, the weight ofthis s&me volume at pressnre p and tem_peraturc 0 would be

-Tr- P 1rY.oJ6 ' TT,,A

a being the coefficient of dilatation ofair which is here taken at .004 in eonse-quence of the constant presence of wateryvapor.

This expresses the weight at the sur_face of the globe. rf transferred to theheight z, the weight would be diminished.in the ratio of the squares of the distancesfrom the center of the earth. 'w'e shouldthen have

W-\-- P 1 R'ruo'*u I+"e (ETa,Substituting in equation 1, dividing by

P and integrating between o and ,; *"get, by callirg the pressure at the lowerstation Po

Ios.+:r*ffi;q '/-:i.

R+,the logarithm being Napierian.

From this we obtain

y2

"-o!#),o*.;,( r*#)But the pressures Po and. P are in directratio of the mercury colurnns which we

will designate by /,,n and h'. These

columns also vary in weight in accord-

ance with the law of inverse squares ofclistance from the earth's center, so that

}:+ ry:*( ,**)'Substituting in the value of z, we have

0.76. (1 + cc?)

wo

1,"**a2 'og ('*#)

I ,. (' *#)

But as z is so very small compared- with

R, ne may replace los. (, * *) by +-AIso #may be neglected.

'We shall then have

0.76 (1 -r':-# 1('. #)"* +'"'?lThe weight W, refers to the height /e,

the lower of the two stations. At the

f-*

33

surface of the earth, this weight

be greater in the ratio ,t #a,

as h is always small comparedthis correction may be rreglected.

would.

Butwith R

But there is another of more importance which shoulcl be taken into aceount.On account of the spheroidal form ofthe globe weight varies wiilr the lati-tude. If G represent the weight of a,

body at latitude AEo, then at any otherlatitude I its .weight, is fo,n,c by multi-plying G by

1-.00265 cos. 2 tThis factor is to be appiiecl to IM, in

the formula. This is accomplished bymultiplying the above value or d by1 + 00265 cos. 2 l.

fn order to simplify the expression ,we

will substitute for 0 the mean between thetemperatures of the upper and lower,rtations, designated by to and , ,. Thefactor L + u0 then beeomes

,' *,,

1+*#since u:.004 ;

and the value of z ma,y be written i, t

0.76 r,: W, 1

If M be used to represent the modulusof the Napierian logarithms we maywrite

,_ 0.76 Jr_ 2(t,+r)qo:I[w ]'- looo f.1(,.;)los +.ry1.

(1 + 0.00265 eos. 2 l)in which the logarithms are of the com-mon kind.

This is La Place's formula. h in theexpression is not the barometric heightdirectly ,-rbserved at the rlpper station,but this height reduced to the tempera,ture of the lower station.

34

1+ 2+'d#') I

The value of ffi, has

,1(,.f-) Ios +**|'.(1 +.00265 cos. 2 l)

ined by trial of the formula uponaltitudes. Ramond in his surveyPyrerrees determined its value18336.

been d.eterm-

f,rro*,of theto be

Er

35

The unknown term ?,

member is determined bvin the secondsrlccessive a,p-

proximations.The first value being

,l_.ot -18336. log. L

/t,(meters)

This being substituted, we m&y have

o -a ,2(to+r)*2-'-t t looo ','_ Fi,ally, these being substituted in the

above value of z we Sut

2,:18886 tog. + .%Pr,* 2,.00265 cos. Zl

+ (z'+ 2M. lg886)#

The terms of this formula areally reduced to tabular form foreal use.

Guyot's formura which is derived fromthis, redueing meters to feet and the co'-stants depending on temperature bcingchanged to aeeord with Fahrenheit'i-scale, is

/,o

h

gener-practi-

z-6A158.6log.

36

I l, _t"+t-AlrI \^ ,OO-)I

I (1 +.00260 cos. 2/)

It z+52252 I \[(t* zoss68-60+rcr.arrco)

The three terms after the first &re the

corrections. The first being that for the

temperature at the two stations' The

seeond is the correction for the force of

gravity dependiog on the latitude'The thircl contains, first the correction

for action of gravity on the mercury

column at the elevabion 2) and seeoncl a

correction required for decrease in d ensi-

ty of air owiog to deerease in action of

gravity at the greater elevation' The

factor s being the approximate differenee

in altitud.e of the stations.Plantamour's formula, which has been

mueh used., differs slightly from Guyot's.The first coefficient is 60384.3. The rJe-

nominator of temperature term is 982.26

and a . separate correction is used- forhumidity of the air.

To use either of these formulas tables

are necessary, of which those prepared

Er*

,3?

by Lieut. Col. 'Williamson* are the mostelaborate.

For the Aneroid in ordinary practice,formulas of much less complexity maybe profitably used. The eorrections de_pending npon the gravity of the mercur.ycolumn would, in any ease, be omitted.The other correetions may in yery nicework be retained. But a correction de-pending on the effect of changes of tem-perature on the metallic work of theinstrumeut should be carefully remem_bered. tr'irst-class Aneroids claim to becompen sated, but a greater portion willneed a eorreetion which the purehasercan determine for himself, by subjectingthe instrument to different temperatureswhile the pressure remains eonstant.

A modification of Guyot's formulaadapted to aneroid work was suggestedin an excellent paper on the use ofthe aneroid, read before the Americ&nSociety of Civil Engineers, in January,1871

x The use of the Barometer on Surveys and. Recon-noisances. By R. s. rvilriamson. New york : D. vanNostrand. London : Trubner & Co.

ryiaH,il:fii0t1

li;{i;r

.i'tl

:

,1.

;i

ii

38

It is

D-6oooo (1og rr-tos r;t(t+ ffij9)D is the difference of altitude in feet.

H and lr, are the barometric read.ings ininches.

T and t are the temperatures of theair at the two stations.

Table II is prepared for the use ofthis formula.

Other formulas wili be given iu anotherchapter.

1

F

ti.

,$l*l

[.

tit, r

i

r*

i

iIr

Ittrir

t

II

II

ItI

rtI

ltI

tI

l

ifa

a

r

h

ti

r

rttI

]kllttrl

Ir

r

t

trI

t

tr

!

lt

I

I

I

IiI

i

i

I

,

'|

:

itL

39

CIIAPTER TIT.

ANEROID BABOMETERS: TEEIR CONSTBUCTION.

Tnn general principle of constructionof all aneroids is the same. A box withflexible sid-es, hermetically sealed, the airhaving been first exhausted, changes itsform as the pressure of the atmospherevaries.

The chief differences in the various,kinds lie in the mechanical devices,, bywhich the motions of the box are ren-dered apparent to the €ye, and. also meas-sured. in such a manner as to allow thecorresponding pressures to be expressedin inches of mercury.

The aneroid was invented about thebeginniog of this eentury, but 'w&s firstmade of a serviceable form by Yidi, in1848. It is substantially the form moqtused. to-day. The yacuum box is a thiulow cylinder, and the motion of the thinflexible head of the cylinder is conve;red

40

by suitable mechanism to the indexhand. Yidi's aneroid is shown in Fig. L.

D is the vacuum box, supporting the up-

right pillar M upon its center. '' A* M;

rises or falis, & corresponding motion isgiven to the plate C. A coun.ter pressure

a

ulIL

is affordedmotion ofand 2to athe figure.

/l i

ri.,iii'lrltlrii;iiil

--l/

IttF ig.2

shaft is conneeted bv a minute chain*with the shaft whicrr carries the indexpointer. It is kept wound to the propertension about this shaft bJ, u nr" spiralhair spring

4t

by the spiral spring S. TheC is conveyed by the links 1little roeker shaft, shown inAn arm, B, attaehecl to this

-\-\

l-:ll

42

A modification of this is shown inFigs. 2 and 3. (See, also, frontispiece).

'Ihis is Naud.et's aneroid, and. i* tn. one

chiefly employed now. It tliffers fromYidi's in the substitution of the thirt

_"{e

43

laminated spring (B in frontispiece) forthe spiral spring (S in Fig. 1).

one of the oldest forms of bon barom-eter and the one to which the name

aneroi,cT is restricted by some writers, jsrepresented in Fis. 4. A reetangulartuhe, from which the air has been perfectly exhausted. is sealed hermeticailp

I

I

h

.'t

$II

ilI

[ffi

L+

and, having been bent into the form rep-

:esented in the figure by cbtl, is made

fast at the mid.dle point b' The varying

pressure of the atmosphere causes the

extremities c and cl loapproach or reeede

from each other' This rnotion is corr'

verted into a to-and'-fro traverse of the

index,byamechanismsrrfflcientlywellexhibitecl bY the diagram' \

This is known as Bourd.on's fotm" Itisnotnowernp}oyeclfordelicatework.The forms of Yidi and Naudel' are' bY

. some writers, clesignated. the holosteri,c

barometers.The graduation of these instruments

ismadetocorrespondwiththeheiglrtofthe mercurial barometer, and is expressed

as inches or millimetet's'The diffi.culties to be met by the rnaker,

in seeuring accuracy of workingr &re those

which arise chiefly from the varying elas-

ticity of the severatr metallic elements

under change of temperature' $reatersimplicity of construction might be pre-

sumed to be at'tende,it with a smaller lia-

bility to a kind of error, for which it t{

L5

exceerJingly difficuit to compensate. Thisis the theory of the Goldschmid Aneroid..

The instrument designed for ordinaryengineering llse is represented by Fig. 5.

The size recommended. by the presentmakers for this serviee is 3& inches indiameter and 2$ rnches high.

The construction is exhibited by Fig.6. The vacuum box, constructed. as be-

fore described., is shown at ct,a,. The mo.

tions of the box. caused. by variations ofatmospheric pressure, are conveyed di,-

rectly to the lever, whose fulcrum is ate" , artd,whose free end. is at e. This end,

projecting through the side of the c&s-

irg and working freely through a slot, isobserved with a magnifJoog lens, and. thereadirrg on the ind.ex Jf Laken. But it isevid"ent that the lever, working withproper ease on its fulcrum, must be sup-plied. with a certain amount of counter-press/.re. This is ingeniously done byaid of the delicate spring e', wbich is-at-tached to the ]ever near the fulcrum.Bearing on the spring is the point of themierometer screw M, whose head is grad-

iI

-

tr

uated to hund.r.dr# and forms the top

l!IHn"-=+ il:EI

l_H-" '|r

of the case. Both lever and spring arefurnished at their extremities with bright

47

metal heads, whose end surfaces lie inthe same plane. The head e, is, unclerordinary conditions, higher than e, asshown in Fig. 6. 'When

a, readirg is tobe taken the top of the case is turnecltrntil e' and. e are side by sidle ; the hori-zontal marks borne on the metallic headsbeing brought to an exact coincidence byaid of a lens (P in FiS. E). The readingof the ineh,es is taken from the scale ff,and of the hundredths from the divisionson the scale around the top of the boxT; a fixed point c being. marked on thecylinder. rn figure 7 the indices exhibita readirg of Zg.Tb inches.

The thermometer F is an importanlpart of the instrument.

rn some of these instruments the scareff bears no reference to the inches of themercurial barometer, but is of an arbi-brary eharaeter, and is different for dif-ferent instruments. The value of thedivisions is determined by comparison_with standard instruments, and. is c&re-fully expressed in tabular form on thecover of the box

48

Somu corrections for temperature andpressure are requirecL in the use of theseinstruments which, although desirable inthe more common forms of aneroid, have

not heretofore been considered. necessal'y.

'fn the latter instrumenis, however, whenof the best construetion, a com,pensati,on

has been effected which rend.ers a correc-tion for temperature unnecessary. Inthe Goldschmid aneroids n.o compensa-

tion is attempted, but each instrument is

furnished rvith a table of eorrectionswhich have been prepared from oJrserva-

tion on stand.ard instruments.Thus, aneroid No. 3187, imPorted

last year) bears on the cover the follow-ing:

COITBECTTON TABLE.

Eor -Diui,si,on. ?or T'emperature.26.0' 0.02 28" to 48o - 0

26.5":-0.03 52"-+0.0127.0': - 0.03 56o: + 0.015

27.5 :-0.02 60o- +0.02528.0- 0 64o:+0.03528.b - +0.03 68o- +0.04:29.0 -+0.06 72"-+0.05

j

r

rtI

iIit!

,

ii

IL

49

-For Di,uosd,ort. -For ?ernperq,ture.29.5, - +0.10 76o_ +0.0730.0 -+0.14 g0 -+0.0930.5 -+0.19 84 -+0.1131.0 -+0.25 88 -+0.18

92" - + 0.15The temperatures are, of course, taken

from the thermometer that forms a partof the instrurnent, and which, when thelatter is carried slung from the shourd.er,may exhibit a temperature considerablyhigher than that of the air.

A smaller and ruder instrument calledthe Pocket Aneroid is made by theZafich manufacturers. It is only 1+inches in diameter and 1] inches high.A bar fastened to the top of the vacuumbox takes the place of the lever in thelarger instrument.

A larger size is also made in which themovements of the vacuum box are di-rectly observed with a compoun_d miero-t11;r"

is no doubt that all urr"roidlneed a careful comparison with standardinstruments or a, series of trials upon

50

known altitudes, in ord.er to determinethe proper corrections. Such trials

should be made at different temp"i,t,rr"*and under different conditions as .to ris.ing or falling at the time of observation

aot

uta-

IL

aoa

,gIL

I

51

The tables of corrections furnished bythe maker eannot well be substituted forthose mad.e by u careful observer deducedfrom systematic work. The air pump,the hot chamber an,iL the freezing boxare convenient, but inadequate substi-tutes for a large number of trials undernormal conditions

ilIl'

ir

I

I

-i'I

-1,

52

CHAPTER IY.

TJAffiil#"T:I;:Ii O--

ometer maJr be used. either as a weatherindicator or in the measurement of alti-tudes. \\'hen used. in the former capa-

city, the Aneroid, especially at sea,, pos-

sesses som.e obvious advantages. Aside

from its superior compaetness of formand its portability, it responds morereadily to the changes in atmospheric

llressure than the Mercury column, and

thereby serves more efficiently to warnthe mariner of sudtlen tempests.

The words Bain-Change-Fair seen

stamped or engraved on the dial of manybarometers have, of course, ro specialsignifi carreq and are now rarely seen on

first-class instruments of either kind. The

probable changes of weather indicatecl bychanges t-rf the barometer are briefly set

fr,rth in the following:

I$

Iili

II

i

i

a

a

tiL

53

NULES tr'OB FORETELLING 'T'IIE WEATI{EB.

A Risin,g Burometer.

A " rapid " rise ind.icates rlnsettlec;tweather.

A " gradual " rise indicates settledweather.

A " rise " with dry air, and" cold in-creasing in summer, indicates wind. fromNorthward ; and if rain has fallen betterweather is to be expected.

A " rise " with moist air, and. a, lowtemperature, indicates wincl and rainfrom Northward.

A " rise " with southerly wind indi-eates fine weather.

A Steacly -Barometer.

With dry air an d- seasonable tempera-ture, indicates a continuance of very lineweather.

A Falli,n g Ban"ornete?".

A " rapid " fall indicates stormyweather. .i+

A 'l rapid " fall, with westerly wind,ind.icates stormy weather from North-ward..

54

A " fallr" with a northerly wind., indi-eates storm, with rain and hail in sum-

mer, and. snow in winter.A " fali," with increased moisture in

the air, and. the heat increasirg, ind.icates

wind and rain from Southward.A " fall " with dry air and cold increas-

iog (in winter) indicates snow.A " fall " after Yery ealm and. warm

weather indicates rain with squallyweather.

It does not require the highest qualityin the mechanism of an Aneroid. to serve

the purpose indicated in the ab-ove

rules.For the &ceurate' m€Bsurement of dif-

ferences of altitude, however, tJre bestskill in construction ancl the most care-

ful atljustment of the parts is indispens-ably necessary. The use of an Aneroid.of even pedium quality will frequentlylead to considerable errors in estimatingheights. It may also be added hcre thatinstruments of the best manufacture inthe hands of observers unacquainted withthe principles involved, will often lead to

55

erroneous conclusions. This is owing inmany cases to a methori adopted by somemakers of adding a circle marke d, feetoutside of the common graduation toinches of mereury.

Many tourists carry Aneroids of thepocket size, ancl eonsult them frequentlywhile traveling, relying upon a, singleobservation of the index for the deter-mination of their altitucle.

If such a circle of feet be engraved. oathe dial plate with the zero mark made tocorrespond with 30 inches of the mercurycolumn, of course every estirnate of alti-tude made as above mentioned. assumesthat at the moment of observation ; thebarometer at the level of the se& would,stand exactly at B0 inches ; a conditiononly realized. occasionally. And the fur_ther cond.ition is also assumed, that thetemperature of the air is of no accountin estimating heights; an assumptionequally at varia,nce with fact. .1r,

rt is onlv an inferior class of Aneroidsthat bear a fixed. graduated circle of feet,with the zero of altitude correspondingto 30 inches of pressure. , F

:I

I

-

56

Prof. Airy, the former Astronolner Royal

of Great Britain, prepa,red a table for the

nse of barometer nrakers-& scale fromwhich is now engraved. on manY EngiishAneroids. It places the zero of altitudeat 31 inches of pressure. This aftbrds

such large numbers for slight elevationsthat the proper use of the rule is sug-

gested to the observer. He is led- tosubtract the trvo reaclings of feet to get

clifferenee in height. But this again as"

sumes that the &Yerage temperature is50" F.

Table I exhibits Prof. Airv's series ofheights.

Some rnakers, designirg to imProve

upon the sirnple construction just d.e-

scribed., have engraved the outer circle

of feet on a movable ring encirclirg thedial, so that when an observer is at anylocality whose height is known, he may

bring the proper mark of the altitudescale against the index pointer.* Then ifthe observer travel.s about over a section

of country, the pointer will indicate withfair approximation for some hours the

altitutle of thq new Positions.

II

- =l&-

ttI

r

I

iI!

I

ii

iI

iI

i

I

i,

L

57

This device is convenient to a skilledobserver who only requires rapid andapproximate results, but to the novice itis misleading in two ways ; first, becausethe temperature is left out of the calcula-tion, and furthermore, such a, use of themovable scale will, at times, involve alarge error, as it is not a scale of equalparts.

Mr. Rogers Field, C. 8., in 1gTB, ap_plied the movable scale to the Aneroid, soas to convert it from a source of inaccu-racy into an aid towards accr\ra,cy. Heempioys the altitude scale proposed bySir G. Airy for temperature b0o, but h;makes it movable so as to adjust it forany other temperature. The shifting ofthe seale into certain fixed positiorr., i*made to answer the same purpose as ifthe original scale were altere,iL to suitvarious temperatures of the air. rn theJournal of tlre lvreteorologi,car Boci,ety forL87 4, JanuarI, Mr. Field says , ,..

" The object aimed at in designirg thisimproved form of Aneroid was, to sim_plify the correet d.etermination of alti-

,'.!

F

t(

IE '#?tliltq lrrl

58

tudes in cases such as ordinarily occur inEng1and, and. the instrument is thereforearranged to suit moderate elevations, say

of 2000 feet and under, and is not in-tended for more considerable heights.

" The Aneroid is graduated for inchesin the usual way on the faee, but thegraduation only extends from 31 inchesto 27 inches so as to preserrre an openscale. The outer movable scale is grad-uated in feet for altitudes, and this grad-uation is laid down by fixing the movablescale with the zero opposite 31 inehes.This is the normal position of the seale

and. it is then correct for a temperatureof 50o. For temperatures below 50o thezero of the scale is moved below 31 inches;for temperatures above 50o, the zero ofthe scale is moved. above 31 inches. Theexact position of the scale for differenttemperatures has been determined partlyby calculation ancl partly by trial, ancl

marked by figrues engraved. on.-the out-side of the Aneroid. fn order to insurethe altitude seale not being shiftecl, afterit has once been set in its proper position

-s_\

59

there is a simple co,trivance for lockingit in the various positions. 'l his consistsof a pin, which fits into a series of notch_es on the outside of the ring carrying theglass. By slightly raising the slass it isfreed from this locking pin, and. can beturned until the ligures eorresponding tothe air temperature are opposite to thepin, when the glass should be depressedso as to relock it, and the scale beeomeseorrect for that temperAture. The atti_tudes are in all cases determined by tak-irg two readings, one at each station,and then subtracting the reading at thelower station from that at the upper.

" It will be seen from the foregoiogd.escription that the movable scale of theinstrument requires to be set for tenr_peratures before taking any observations,and must not be shifted during the prog-ress of the observations.

" This may appear aL first sight as adefect, inasmuch as the temperature pfthe air may alter during the progress ofthe observations ; but practically it willnot be found to be any drawback in the

Ih

60

case of moderate altitudes, as small vari-ations of temperature will not appreciatrlyaffect the result. A variation of 5o oftempcrature gives only about 1 per cent.variatiorr in the altitude, an amount thatwould und-er or,C.inarv circumstances beinappreciable, so that as long as the tem-perature does not vary d.uring the courseof the observations more than 5o fromthat at which the instrument is set, theresults may be accepted as correct, and,generally speaking, even a greater varia-tion than this, say 6o or 8o, would bepractically of no importance. Of course,if it should be found aL any time thatthe temperature has varied considerably,during the course of the observations,fqom that at which the instrument wasset, this variation can be allowed for bycalculation in the usual way."

The principle of allowing for variationof temperatures of the air by shifting thealtitude scale is not theoretically accurate,but suffrciently so for practicul p..iposes.For aititudes within the range of the in-strument (say 3000 feet and under) andi

iii

ifl,lilill1;

il1t

t

It

i

I

i

i

tIi

IL

61

temperatures betrveen 80" ancl 70", tirernaximum error from nsin ^ the shiftedscale, instead of the ealcuiatio,, is only2 feet, which is inappreciable on ihescale. The same principle might evenbe appliecl to altitudes ,p to 6000 feet,as the maximum error would be only 10feet. tr'or considerable elevations, how_ever, the variations of the temperaturebetween the base and the summit wouldinterfere with the application of the prin-ciple.

I{evertheless, thp best plan i'-q to clis-pense with altitutle seales, whether fixeclor moyable, and to calculate the rreights.simple ru]-es, giving rnore reliable r.es*ltsthan the attached seales, are at the ser.-vice of those who need easy processes.Among these are the following :

-Mrte the rdse or fall of the burontetet,,in, hunclrerlths oJ' u,rt ,inch., ott Ttus.si,ngJtrom one stat,iot;z to tlte othrr, _r. mztltiplyby 9. I'h,e product z,s tlte clifferelLce ,Lalti,tucle dn feet

This is for ordinary ternperatures andpressures. If the pressure is below 26

62

inches or the temperature above 70", use1t) for a multiplier.

A higher degree of accuracy is obtainedby using the multiplier obtained from thefoliowing' table prepared by i\l r. G J.

lry:_I'Iea,n tempe,;; F,*I- -l;tr* I

*Ii.*o p.."...,;;;Ti* L; il 1,,. i io.g , o:a 1o:8: ':

ifli:, i,tfl a fl?'fl $:'flfil$,fi

To find the difference in height be-tween two stations : ?on,cl the nleq?tpressura ,' also the mea,?L tencytcrature.1'/te number i,n the table corre,spondon,gfut these tuso nbeans, i,f multipli,ed, by thetl ffire??,ee of the barornetric p?"essures ,in,

hu,ndredths of an ,inc/c, u:ill gi,ue $he dr,f-lference ,in alt,itude aery nearly.

In the absence of a table to aid incomputation, but having an Aneroid withthe scale of feet, use the formula,

D-ssoooffiti

l,l{,iLiiflr

i$it:ttitlrlii

lj't

63

adding ato of the estimated altitude forevery degree, the auerage temperature isabove 55o, and subtracting a like amountwhen it is below. I), i* the difference ofaltitude in feet; H and h are the read-ings i,n feet from the Aneroid scale. Thisgives fair approxirnations up to 3000feet.

For aecurate results use one of thefollowing methods: I{aviog Airy's table(Table 1) and an Aneroid carefully grad-uated. to inches ; Take the readi,nrl in'inches of the baromteri,c scale at botlulower ancl upper stations I t,l&t the [em-pera,ture at both stati,ott,s., ?in,cl frontthe table the hei,ghts 'itt, /eet corresponcl-ing to the baronr,eter rer.td'in gs. Su,btractthem ancl multiply the rernainder by

T+r-100-To-oo '

The complete formula is

D-(H-l,) (r*I1iffiolg)T and t are the observed temperutorl* ;

H and /t, are the heights in feet takenfrom the table.

itrluiHlnitlti i.rlfitlli i'lIti. i,lllt

I t.r

iill)lil

rt{'ll

, ."i

r il

' ll

,ii, iN

itt+il

l*,tr:{:

I

I$4

tiIi

.i.

I-1t

.It,|

i

.t

{.:

:tT

:.ll.xrl'?{.{{Ji

i

L

64

fn the absenee of this table. but witha table of logarithms at hand, the baro-metric heights in inches are to be taken,and the followirg formula used :

D-60000 (log. B-log. r.)

(t*I'+J-60r\^-=oo )'

B and D are the barometric readings ininches i D, T ancl I as in the other for-mulas. (See Table II.)

To avoid error from the constantchanges in barometric pressure, the ob-servations should be simultaneous. Thisis aeeomplished in the best manner byusing two instruments, and requires,rvhen the distance between the stationsis considerable, two observers. Withone instrument only, Iarge errors areavoided by repeatiog the observation atthc first station after taking that at the2d station, and assuming that any changein barometric pressure that has oegurredhas been gradual during the absenee.

When it is impracticable to repeat theobservation at the first station, the error

65

which, in c&se of a, changing pressure'might be a large one, may be reduced. ifthe observation at the 2d station be con-tinued for an hour or two, or until therate of change can be estimated ancl aproportionate eorreetion applied.

Many Aneroids marked,,eompensatecl,,exhibit a sensible, change when the tem_perature is variecl; such instruments ilIaybe servieeable and quite aeeurate ifallowance be made for the error. of theinstrument. This correction the ownerhad better determine by experiment. Itis easy to subject the Aneroid to suchvariation of terrrperature as shall embr aeethe range at rvhich it is hkely to be used,and. the moyement of the index for each10" or 20o of temperature recorded.

Aneroids require to be compared fromtime to time with a good mercurial baro-meter. While making such comparisons,it is well to remember that the rnercurialeolumn and the scale by which it* ismeasured both require eorreetirg, andthat during times of rapid changes, inatmospheric pressure, the Aneroid shows

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such changes more readily than themercurial barometer. (See Table IY.)

In measuring heights with the Aner-oid care should be taken that the instru-ment is not influenced by the heat of thehand nor by the tlirect rays from the8Un.

The instrument should always be tap-ped gently with the finger at the moment'of taking an observation. It shouldalso be held in the same position forboth observations ; preferablv with theface horizontal.

Considerable care is also required todetermine exactly where the indexpoints. It is best accomplished by sighLiog along the pointer, using one eye onlyfor the purpose.

The followiog example will illustratethe use of the tables.

Barometer at Station A30.04 Thermometer ?8''( B 28.69 (c 65"

From Table I we find height* corre-spondirg to reading at A is 857 feet.The height for B is 2L20 feet.

The approximate height is 2120-88?

67

:L263 feet; but the sum of the tempera_tures is 148o. An additionar eorrectionof 16*r is, ther efore, to be applied to theabove difference; flris is Ei' feet. Thetotal estimated difference of altitude isthen 1263 + 54_ tBlT feet.

The formula directly applied is

D:(zu2o-8b8) (r*I#*ry)_ 1317.21

_ Applying the logarithmic formula wehave:

Lo-g. B 80.04:L.477700b 28.68:L.457579

Log. B-Log. b_0.0Z0LZt

D : 60000 (.ozotzrl (r . W)-L207.26x1s%ro _ 1B1g feet.

As before remarked, the GordschmidAneroid requires that both the iempera_ture of the air and of the instrument becarefully taken. Two etamples of altfttud'es taken with the instrument prev-iously referred to (No. Blgz) wil serveto show the kind. of correction neeess aW,

It.

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and as both examples apply to the same

mountain (Kiarsarge of ConwaY, N' H'')

theywilltogetherindicatethecharacterof the instrument.

Ex. I.-Julv 9ru, 1881'

Station.F.i

,g

26

6..qJ ilJ

PC

(-- Fr

Fryeb'g.Mt.Kitrr-

sarge.. i1. 00r. rr

Ex. Il.-Aucusr 9tu, 1881'

In both these examples another read.-

ing would have b:u1 taken at Fryeburg-

orp the return, if the better alternative of;

trih! tl

iHI r.il1It,1,

tl*F-

l1ub iTemn. iCorrect'nsLl I I .

or-{ I : .rr1 I I i t-r{ AFliliti E Yf;iils,f, fi

.51:66'166' +.04 -.1(iti

.75174'l74'+.06 -.0:lii

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l.l;li :

lr;

il I

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ifrl

;{ I

Ft" I.*l,.n lti",r lll!1 Iil,tL I

iillLr I

iHi I

ffil

:

69

securing hourly readings of a stationarybarometer at Pryeburg had not been fol-lowed. On July gth there \vas no changein the Fryeburg barometer. On Augustgth the follon irg reading.s \rere taken atFryeburg:

7 L. 1\r. 2e.53g (( 29.52

10 c( 29.5L5L2 .c 29.46

1 P. M. 29.462 c( 29.4553 (( 29.40

As this set of o'bservations indicates afall of ,07 in the interval between thebase and. summit readings, it becornesnecessary to make another eorreetion tothe last eolumn.

correeting the first reacling to accordwith the faIl indicatecl by the stationarybarometer, ,^'e set after all correetions:

Irryeburg, 29.39.Mt. Kiarsarge, 2B.S1..

The logarithmic formula for estirnatingheights from barometric observations.*is

D-6oooo(rog.B-los. 14 (+ =ffiry)

in which

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D . difference in altitucle in feet.B-height of barometer in inches at

lower station.b -height of barometer in inches at

upper station.T and t are the temperatures of the air

in Fahrenheit degrees.Applying this formula to our first ex-

ample we have:

D - 60000( L.47 202 - L. 427 8L)

(r*f4#)-288Ttt.The second example gives:

D - 60000 (1.46820 - L.4234L)

(r* 121:60 ) - 2881 rt.

As the station at Fryeburg is 434 feetabove the sea, the estimated total heightof Kiarsarge would be, in one ease, 3321feet, and in the other 3315 feet.

Prof. Airy's table gives 3319 and 3314from the same data. ^a

The instrument employed in the abovemea,surements has been used in ma,ny

other cases of altitudes from 3000 to

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4000 feet. An eror of about 2 per cent,in excess has been detected in those c&seswhere the altitude has been measured bymore aecurate means. It seems likelythat the special correction table need.ssoilre slight revision.

The followirg measurement was madewith an aneroid only 1$ inches diameber,made by Casella.

Neversink, Sullivan Co., N. y., and.Slide }fountain, Illster Co.

j',-* l*.ffil** I r.N*.*#-lr ^*i-8 64 i-*Ttv Clutr Camp. i11 .( | zz .gz i Zg"Slide Mountain.

14 p.M. I zs. ez i Ur"

i ut.iTab.I.I

21 5828534931

D-(4e31-2158)(m,-2773 X 1.03 - 2856 feet.

As Neversink had been satisfactorilydetermined to be 1350 feet above these&, the total height of Slide Mount-ain is estimated from this observationto have an altitude of 420G feet.

k

72

(Nom).-Beturn observations were

made only at the camp of the FIy Club'

Between 11 e. m. and 9 P. Ur', no change

occurred in the barometer.

The Tri,bune rePort, however, indi-cates a rise on this date of .07 between

7 and 11 A. M. If such a change was

felt in this region, then the calculated

height of the mountain is too low by at

least 60 feet. On the other hancl, a'

height given by railway survey in this

vicinity, (Johnson's }Iill) near the camp,

seems to confirm the fignres given here'

A-lso, the height of Hejsinger Nctch,'taken incid entally on this excllrsion, was

estimatecl at 2660 {eet. Guyot makes

tlre Notch 2677 and the summit of siideMount an 4205 feet.

The height of the base at Neversink

was estabiisherl by four observations,

between Nerv York Buy and- this base,

and \yas confrrmed by comparison withthe height of the railway track lat lrib-erty, six miles southwest.

73

to Blue }lountain, AugustNeversink19, 1990.

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N*.".trk I

Blue Mt. .l\Ieversink I

I

10 30 P. ]r. 28. 903 P ]r. i 2i.476 c'

l2885

60' 2g . g7 1 94160 27 .+i 3295lo+'ilir

rime ,fd1! r 3?,1_#r.

Ditr-(B2eb-ie41r(r"#)- 1354 x 1. 022

- 1384 feet above Neversink or2734 feet above the sea.

The eorreetecl readirg lvoulcl be 28.82b,if the seeond reading hacl been rniclwayin point of time betrveen the first andlast.

This mountain is in Ulster Co., I{. Y.Long. 74" 35 W. ancl Lat. 4L" 52 N.

Neversink and Denman Mountains(Casella Aneroid). Supternber 11, 1880.

Time.

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Ditr - (BG. sl-leoe)(t * uq * f3*t'9)

-1665 x 1. 026

- 1708 feet above Neversink or3058 feet above the sea.

This mountain is S. S. W. of SlideMountain, and near Claraville. Long.74o 28'; Lat. 41" 53' I{.

Fryeburg, Me., and Kiarsarge Mount-ain, N, H.-Fryeburg base 434 feetabove the sea, July gth, 1881.

(Casella Aneroi,tl)

]rr*.. ,n.fo1l,'*. I ,.

Frveburg. . . . . ., 6e. rnr.i ?g.qq i qq:Kiarsargt ..... 1p. n.; 26.83 '174'

I n,.lTab.I.

I rzsa, egas

(Note)-Barometer at FrYeburg re-

mained stationaty.

Diff. - 2705" (t * ?4

i33o tol;

-2813 feetor 3247 feet above the se&.

75

Fryeburg, M.., and lVIt. Kiarsarg€rN. H. (second survey) August L7th,1891.

, (Casella, Anerotd.\,-i ut.,Tab. I.I

lt'*'' lu,f,i,llss r.

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Fryeburg. .

Mt. Kiaisarge. . .

9 e. rvr, I Zg .203 r. u. i 26.81

59',I 116953' I 3958

I

(Note)-Barometer at Fryeburg sta-tionary till 4 P. IU.

Diff. -2,789 X 1.0L2-2822 feet.Tota1 ht. - 3256 feet above the sea.Height of this summit aeeording to the

Geological Survcy is 3251 feet.

Liberty Hill, N. H. (near Laconia),and Mt. Belknap.-The base station wasat Mr. Rowe's 1130 feet above the se&,July gth, 1878.

(Casello, Barometer.)

Bar.Readings.

L-ib,qtyHtlL*l ,8Jd

rn I ut. .,,ro I

Tab. I.

-t-

82' | 205478" I 3285[t. Bblknap. . . .l 27 .dg

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76

As the interval betweeft the observa'tions was very short, and the generalpressure sensibly stationtury, no recordwas made of the time nor the returnreading.

Ditr - (3235 - 2054) (, * 8Sfr;Uo

-L252 feetor 2382 feet above the sea.

(Note;-An ayerage of three measure-

ments of this mountain gave 2392 feet.

The other observations yielding 2369

and 2425 ft. respectively.The height given in the Guide Books

quoted from the Geological Survey is239+ feet.

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77

CHAPTI]R Y.

"TH:Ti#^ffiil: # ;:*ff:il "".Dealers in good aneroids are generally

prepared to testify in regard to the per-forrnance of their instruments rvhentested by the air pump. Comparisontables frequently accompany first classinstruments which show the differencesbetween the aneroid referred to and astand.ard mercurial barometer subn:ittedto the same exhaustion.

The buyer may reasonably ask, there-fore, that such a test may be ma,ile if ithas not been previously done.

The best English aneroids are nowmarke d, compert,satecl, and are presumablyfree from error arising from changes oftemperature in the instrument itself,.iYhether such be the case can readily bedetermined, by the owner of the instru-ment subjecting it to th" action of t

78

freezing mixture and then of a dryingoven, while the normal pressure remainsthe sa,me. A thermometer should be

placed beside the aneroid during thetrial. A range of temperature from 15o

F. to L75" F, rnay easily be produced,and a co-effi.cient of correction if the in-strument is not compensated, maI be

determined.The grad.uations of a good instrument

are neatly engraYed. on the dial.The divisions corresponding to the

inches and fractions of a mercurial bar-ometer are the only essential ones. Thecircle of feet, whether movable or fixecl,is & convenienee of secondary import-*ii'

u,o aneroid bears a fixed circle offeet with the zero mark correspond"ing tothe 3O-inch point of the other scale, theprobabilities are that the instrument isnot from one of the best makers.

Excellent aneroids are now madb wii;hdial plates only 2$ inches in diameter.The Casella barometer referred to in theexamples has a, diameter of only L*

s.l-Ei

tr&ss

tr

ffiffitfi

iii

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,79inches. Of course the smaller fractionsof an inch are more easily read on dialsof 4 inches in diameter ; but the porta-bility of the smaller instruments reeom-mends them for the use of the topogra-pher, and the medium size, which is fromZfr Lo 2$ inches, is now most in demandfor surveyor's work.

The aneroids in any considerableeollection will be found to be vari-ously graduate,il; some of them capableof indicatirg a fall of pressure to Z0inches, corresponding to a height of over11,000 feet, while many are designed forcontinual use below 3,000 feet of alti-tude. In two instruments of the s&mediameter, but differing as above, it isclear that the latter will have the largerscale divisions, and rvill, therefore, bethe better instrument to use at th,elou)er alti,tudes.

It should be carefully rememberedthat all aneroids vary in their readings,with the position in which they are helcl;reading always a little higher with thedial horizontal (face uppermost), than

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rvhen it is vertical. The difference isclearly owing to the direct weight of themechanism exerted on the vacuum box.There is no objection to allowing thisweight to be always added, but the prac-tice of the observer should be uniform,ancl to read from the horizontal clial isprobably the most convenient practice.

A tap with the fi.nger just before [ut-irg the reading is requirecl to bring thesprings to their proper bearing. Also,in case of rapid. ascents, as some aneroidswill not, at the moment of attaining analtitude, indicate the entire falI of press-ure, a few minutes' delay is necessary.

The pointer should be fine and veryclose to the graduated seale, ancl thereading should be taken by lookirg alongthe direction of the pointer.

For ordinary work it shbul,it not beconsidered important to adjust theaneroid to an absolute agreemsrt withthe mercurial barometer. The differencebetween the readings may be noted, butto force the aneroid to an agireement by

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:rid of th; adjusiiog serew is a question-able practice.

Whenever comparison n ith the mer-cury column is made, the reduction forthe latter by Table l should be earefullyobserved..

In the use of either form of Aneroid,whether it has been furnished with acorrection table or not, the observershould take early means to become ac-quainted with its limits of error undervarious conditions of temperature orpressure. Repeated measurements of a

knor,vn altitude afford good data for suchinformation, but direct comparisons, fora long time, with a stand.ard cisternbarometer will yield, with a minimum oflabor, the greatest number of compari-SONS.

For the method of dealing with suchdata to determine correction coefficients,the reader is referred. to the larger treati-ses, the most exhaustive of which, prob*bly, is " Die Aneroide," by Josef Ildltschl (Alfred Holder, Yienna, L872).

X'or ordinary use of a, single instru-

E2

ment, however, the corrections, if anyare necessary, are determined with suffi-cient accuracy by the exercise of ordi-nary skill and patience ; skill here imply-irg, also, systematic trial.

Some of the sources of error in meas-uring altitudes, which are not to be elimi-nated by any adjustment or correction ofinstruments ) are clearly stated by Prof.Elias Loomis, in a paper read before theNational Academy of Sciences, April 19,

1881.('The Iraplace formula assumes that

the atmosphere has attained a, conditionof equilibrium, and. in such a case it givesthe reduction to sea level with tolerableaccuracy. The average of a long seriesof observations represents a,pproximate-Iy such a condition of equilibrium ; butin the daily observations this equilibriumis very much disturbed. The mean be-tween the temperatures at the upperand. lower stations does not represent theavera,ge temperature of the intermediateeolumn of air; and when the atmos-

la

phere is in rapid motion the dowuward

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pressure is modified by the earth's rotation, in a m&nner not represented by theLaplace formula. There is no doubtthat the formulre of reduction now em-ployed may be consid.erably improved;but it does not seem possible that anysingle formula, with constant coeffi.eients,should provide for the immense varieiyof conditions which prevail in the leigh-borhood of mountain stations; and wemay be compelled for eaeh mountain re-gion to a,ilopt tables founded upon a di-rect comparison of observations madrl atstations of different elevations ancl notvery remote from each other. "

The followiog remarks bearing Llponthe same subjeet are from &n article byJ. Allan Brown, F. R. S., on ,, PeriodicOscillation s of Barometric Pressuro,"published in Nature in April, 1881 :

Sed.gwick has said, [,, To explain dif-ficulties in these question s " (relating topressure and temperature) ,, the atmes.pheric strata hav'e been shuffi.ecl in aecordanee with laboratory experience."]

" If we suppose that the attraction of

84

gravity is not the only attractron whicl-raffects the pressure of the atmosphere,but that this pressure varies throughsome other 'atfuactiog force-such as anelectri c attraction of the sun dependiogupon the varying humidity of the air, anclthis aga,in dependiog on its tempera-ture, we should lind another method ofrelating the two variations ryhich doesnot exist if gravitation alone is employed.It is quite certain that many physicistswill not admit the iclea of an electric at-traction on our atmosphere in the presentstate of our knowledgu, hence the effortsto ruake expansion, and a shuffiiog of theatmospheric strata suffice. We mustnot, horn'ever, in our ignorance, attemptto force ' conclusions in opposition tofacts, and if these can be satisf.ed moreeasiiy and witir greater probabitities inits favor by the aicl of the hypothesis ofan eiectric attraction of the sun, thathypothesis will have a better chim toacceptance than the other. f shall herenote a few facts which eannot be explain-ed by thermic actions.

fi

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(t 1. tr have shown that, on the averag.e cfma,ny years' observation in our latitudes,the mean pressure diminishes at the rateof 0".038 of mereury for every one hun-dred miles \ve proceecl toward the north.This has been callecl a gradient from thethe similar term usecl in railway slopes:but it is no slope, it is a level of a sLlr-face of equilibrium like that of the sea.rt is the mean heights of the barometerat the sea leve1 which indicate the form,if rve may so saJr, of the equilibrating at-mosphere.

" 2. fn Inclia rve have seerl that the at-mospheric pressure osciliates at, eaehstation eyen when these a.e cluite near toeach other, inclependently of the knownlaws of equilibrium of gases. When weturn to the serui di,rnal oscillation ofthe barometer we are only amused at theattempts made to explain it by shufflingthe atmospheric strata. Nothing can bemore certain than th,at the theories ofexpansion, or resistanee to expansion ancloverflowr are the vain efforts to make thelaws of nature agree with a theory. Over

ri6

trd gleat ocean wil;hin the tropics, wherethe diurnal variations of temperature aresmall and the air is absolutely withoutperceptible currents for days together,the barometer rises and falls a tenth ofa,n incir twice in twenty-four hours withthe regularity of the solar clock. Theaction of the sun on the whole atmos-phere which produces this movementvaries chiefly during the .lry hours at in-ian,il stations with the temperature oscil-lation, so that, e s in the case of theannual variation, the fail of thebarometerat 4 P. Nf . is greatei in the same latitucleas the temperature is higher. Thisvariation occurs durirrg the most com-plete calms; the smoke rises verticallyfrom the plain of Tinnevelly ; no currentis visible in the motion of the clouds; yetthe barometer falls at four in the morn-irg as it did at four in the afternoon,only it falls less."

It seems probable that the use*of theAneroid will soon beeome more widelyextended, and that engineers, when madefa,mili,rr with the qualities of well-ma,ite

87

irrJtroments, will welcome so valuable r nairl in preliminary surveys. The concli--*ioons of satisfactory work with baro-meters are certainly peculiar, and to fie1.1workers familiar only with the level ancltransit, m&I seem unique. But rn lienthe con,ilitions are fully understood, theengineer may easily take precautionswhich will avoid too large errors, andconduct suryeys in hilly regions withaeelerity not heretofore attained.

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TABLE I.FOR ESTIMATING H.EIGHTS BY TIIE ANEROID.

Take readings of the barometer and thermom-eter at both stations ; flnd in the table theheights corresponding to the barometricreaclings, and subtract them. Multiply the

remainder by , "Tffilqo T and r being

the temperatures, the prodtrct wiII be the

difference in altitude

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tltittHl1lrlrlrl,'lrll[-itli

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Barometer I -,

i1;ii,# | Heights "*ll#'ryI =:Inclres31 .0030 9980.9880.9730. 9680 .9530 .9430.9330 92;0 9130.9030.8930 8830 .8730 .8630 8530.8430.8330.82

Feet.00I

182735M53627T808897

106115L24133L42151160

30. 8130"8030 .79

Inches. i Feet.168177186

30. 7830.7730.7630. 7530.7430,?330.72s0 .7130. 7030. 6930.6830.6730.6630 .65s0.64

1952032L222L230239247256265274283292301310318t eo. og | 827

89

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Barometer I ril:;fiil;: rreights.

tr'eet.336345354363al +;\OJ;3813e03994074t642543444345246147047s483497506bIi)524RODrrdt)51255155956957858759060i613

Barometer TY.r.Readinss. : I]elgnts'

Inche.30 3030 2C

30.2830.2';30 2{'30. 2530 2430.2330.2230 2130.2030. 1930.1830.1730 1630.1530. 1430 1330 1230. 1130 1030. 0930 0830. 0730 0630 0530.0430 0330.0230 01ir0 0039 99

Inc ires.30. 6230 6130 6030.5930 5830 5730. 5630. 5530 5430. 5330. 5230 5130 5030. 4930. 4830.4730. 4630.4530 .4430 .4330 1230. 4130 4030. 3930 3830.37t]0. 3630 3530. 343C. 3330 32110.31

tr'eet.6226316106496586676766858s4?037L2721730740749758rtlrrlO785794803B1?821830839849857866875884893903

90

Ileights.

Fcet.1205L2t4722,L1233721t1251126012691 278128712961 30513141:i241333It4213521361137013791"3891398I 408L4t7L4261435L4457451

-* L4647473L4821491

I

Baromeler I rffi;,i"r,;;;: I rreights'

l-

Inches. I Feet.2s eB i gtt29 97 i 920

BarometerIleatlings.

29 9629 952s.94

Inehes.29. 6629.6529 .6429 .6329 .$229.6129 .6029.5929.5829 .5729. 5629.5529.5 t

29. 5325.5229.ltl29. 5029.4929 .4829.4729.482g .4529.4429 .4329 4229.4729 .4029. 3929.3829.3729. e629.35

929938s47

29 9329 .9229.9129.902) E929.8829.8729 .8629.8529 8429 .8329. 8229. Bl"29.8029 .7s29. 7829 .7729 .7629 7529.7429.7329 7229 .7t29 .7029 6929 6829.67

95696597698599{

100210121021103010391019105810671076108510941 r031 1131r227L3217411 150115 )

1 169117711.q81195

BarometerRead ings.

Inches2e .3429 3329. 322e 3129. 302g 2929 282s 2729.2629.2529.2429 .23q() f)()h/ aJ . A),<)

29 2729 2029.1929.1829 7729 7629.1529 1429.1329.1229 1l29.1029 0929 0.329 0i29 C629.0529 .0429.03

q1

Ir

-

Ifeights. i

li'r Barometeri E;r".i"i;;:' Ileights.Readings.

Feet.1 5001 50915191528153715461 5561565757 415831593160316121621I 630163916491658166816i716871 696170617151 72517'J417 4377 527762t77t1 7811790

fnehgs.29 0229.0129.0028.9128 9828.9728. 9628 9528.94i8.9328.9228 9128. 9028 8928. 8828 8728.8628 8528 8428. 8328 8328.8128 8028. ?928.7828 .7728.7628. 7528.7428 ?328.7228 71

Feet.179918091818182 71 8371 84618561 86518751 884189419031 91319221931194t1950196019691979198819 982007201620262035204420542063

't:

2A7320822091

9z

Heights.

Feet.240724162426243524452455

'

24642474248324932508251225222531254125512567257A258025902600260926192628263826482653

..2667*z6w

268720962706

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lit:Illl:littrtIFI}aa

Dtir,'B-rrTE'rItiEi

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Barometeri -r"n."tiiil;t. I

rreigh ts'

Inches.28. 7028.6928. 6828. 6728. 6628 6528. 6428. 6328.6228 6128.6028. 5988. 5328 5728. 5688. 55

'J8 54E8 53,',)8.52tl8. 11*8. 5028. 4e28.4828 .4728 .4t)28 4528.M28.4328.4228.4188.4098.3e '

Feet.210127Lt2t2027292139214921582168277721 862196220522752224223422432253226322722282229123012310232023292339234923582368237823872397

' tpF--

BarometerReadings.

Inches.28 3828.3728.3628. 3528,3428 3328.3228 3128.3028. 2928.2828.2728.2628. 2528.2428. 2328 2228.2128 ;2028. 1928.1828 .7728 1628.1528 t428. 1328.7228.1128. 1028.0928. 0828.07

93

I

Barometer I

Readings. I

-__l

Heights. Barometer a"R:;",tTd: Heightu

Inches.28 0628. 0528 0428.0328.0228 0128.0027 .9927. 9827 9727 .9627 .9527 .9427 9327 .9227 9127 9027 .8927. 8827 8727 .8627.8527 .8427.8327 .8227 .8127.8027 .7927 .7827 .7727"7627 .75

Feet.27152726273527 453'r aD

276it277427842794280428132823283328432853286328732882289229012911292l2930294029502960296929792989299930093019

fnches.27 .71()-^j)pt. tD2T 7227 .7127 .7027.6927 .6827.6727 .6627 .6527 .6427 .6327 .6227.t;727.6027 .5927 .5827 ,5727. 5627 b527 .5427 .5327 .5227 5t27 .5027.4927.4827.4727.4627.4527 .4427 .43

Feet.':i029

303930483059306830?8308?30973107311?3126313631463156316631?63186319632063216322532353245325532658275328532953305'331533253385

iL

94

i

I

I

I

I

II

;

l

i

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iI

I

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I

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I

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III

tII

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I

Hm;::i rr'isnt*'

Feet.38453355 ._,

336533753334339434043474342434343444345434643474348434943504351435243534354435543561357+35843594360436143624363436443654

In ches.27 .4227.4L27.4027 .3927.38iry Dr'/pa.ot

27.3627 .3527 .3427 .3327 .3227 .3t27 .3027 2927 .2827 .2727 .2627 .2527 .2427 .23qry qoH a . trJAJ

27 .2127 .2027 7927.1827 7727 .7627 .7527 .7427 .7327 L227 .71

BarometerReadings. Ileights

Inches.2?. 1027 .0927.0827 .0727 .0627 .0527 .0427 .0327 .0227 .0t27 0026 9926. 9826 .9726 .9626. 9526.9426 .9326.9226.9126. s026 .8926 BB26.8726.8626 8526 .8426.8326.8226.8126.8026.79

Feet.

3ffi36853695370537153725373537 4537553765.I'ryF F5i rO3785i]795, 380638163820383038463Bi63866387ii[i88Li3897390',i391 7392 iti03B'4 Bg4g395830683978

95

Br*o*.t., I r^'R.;",ii;;.:, Heishts'

Inches.26 .7826 .7726.7626 7526.7426 .7326.7226.7126.7026.6926.6826 . rt726.6626.6526 .6426 6326 .6226 .8726 . tiO

26.5926.5826 .5726.5626.5526 .5426.5326 .5226 .5126.5026 .4926.4826.47

Feet.3988399940094019403040404050406040704081409 r4taL47114722413247424t5241 63417341 8341934203421342234?334244425442644274428442944304

B1;'tr$:l*u*o,..Inehes.26. 4626 .4526.4426.4326 "4226.4t26 .4026. 3926.3826.3726. 3626.3526.3426.3326,3226.3126.3026.2926.2826 .2726.2626.2526.2426.2326.2226.2126.2026. 1926. 1826 .7726. 1626. 15

Feet.431543264336434743574368437843884399,L409

4Llg4430444044504461447)44824+924502451345234533454445544565457545854596460646L746274638

iL

96

i

I

Barometerl r^'n.r"tii,igi., Heights' Buro*"tu, i

PryI Ileights.

Inctres.26.7426. 1326.7226.1126.1026.0926.0826.0726.0626.0526.0426.0326.0226.0126.0025. 9925"9825 "9725 .9625.9525.s425.9325.9225"9125.9025 .8925 .8825.8725.8625. 8525. 8425.83

Feet.464846584669467946904700477L4721,4731474247524763477347844794480548154826483648474857486B4878488948994910492049314941495249624s73

Inche *.25.8225.8125.8025.7925. ?825 .7725.7625.75

Feet.49834994500450145025503650465057506750785088509951105L215132511251535L645L7451855195520652165227523i53{B525952705281529L53025312

25.74 I

25. 7325.72 i

25.7L i

25 .70 i

25 .6925.682d.6725 .6625. 6525 "6425. 6325.6225.6125. 6025.5925. 5825.5725.56ZO. Ct)25.5425.5825.5225.51

I

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Ba*o*.t., I r"nr-oHgi. i

rreights'

Feet.5323533353445355oooD5376538753975408541 I51295440545154625+7354836494DOUt)

5516552755375548555955705581COUE

560256135624563556465657

Inches25. 5025,4925.4825.4725.4625.4525.4425.4325.4225.4125.4025 3995.3885.3725.3625.3525.34oR .) -tPU . O?)

25.3225. 3125.3025.2925. 2825.2725.2625.2525.2425.2325.2225.2L25.2025.19

Iuches.25.1825.7725 1625.1525.1425. 1325.7225.1125. 1025.0925. 0B25 0725.0625.0525.0425.0325.0225.0125. 002+.9924 9824.9724.9624.9524.9424"9324.s224.9t24.s024. 8924. 8824.97

Feet.5668567956895700571 157225733574457545?655778578757985809582058315842585358635874588558965907591 85929594059505962597t598359946005

b

Bn rometerReadings.

Inches.24. 8624. 8524.8424. 8324. 8224.8124. 802+. ?924. ?824.*t721.7621.7524.7424.7324 .7224.7L24.702+ "6924.6824.6724 6624.6524.6124.6324.6224.6t24.6024.5924. 5824.5724.5624.55

98

Heights.

Feet.60166027603860496060607160826093610461 15

6126613?61486159617061816L92620362746225623662476258626962806291630263136324633563466357

BarometeReadings.

Inches.24.5424.5324.522+.5724.5024.4s24.4824 .4724.4824 4524.4424.4324.4224 "4L24.4024.3924. 3824.3724.3624.3524.3424.3324.3224.3t24.3024.2924.2824.2724"2624.2524.2424.23

tr'eet.636863796390640164t264246435644664586469648064916503651465256536654765596570658165926603661566266637664866596671

''.,6692

669367056716

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BarometerRcadings.

Inches.24.2224.2124.2024.1924.1824.t724.7624.7524.1424.L324.1224.7724.7024.0924. 0824.0724.0624.0524.0424.0324.0224.0124 .0023. 9923.9823.s723.9623 9523.9423.9323.92oo 01NU..J-L

Heights.

Feet.6i2767386750676167726783679568066817682868406851686268?3688568966907691969306941695369646976698769997010702270337045705670687079

99

I

Barometer | .r

R;;,tds;: i rreights.i_.

Inches.23.9023 .8923 .8823 .8723"8623.8523.8423 .8323.8223.8123 .8023.7923.7823.7723 7623 .7523 74oa POpo.,a)

23 .7223. ?123.7023. €923 .6823.6723 .6623 .6523.6423 6323.6223. 6123.6023.59

Feet.709071017113712171357 1467757716871807tg77203721472267237r7249

7261727272837294730573167327733973507382737473867398

".

7409742174337 415

i

I

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&

100

Baromet., I

Readings. I_-_lHeights. IIeight,s.

Inehes.23.5823 5723.5623 5523. 5423.5333.5223.5123 .5023 .4923.48!3.4723.4623.4523 4423.4323 4223.4128.4023. 3923.3823. 3723.3623.3523.3423.3323.3223.3128.3023.2923 2823.27

n'eet.74567468748074927503,/DI{)

7527753975507562757 475857597?609762176337644?656766776797690?70277t37725773677 48775977717782ws378057817

Inch e.q.

23.2623.2523 2423.2323.2223.2723.2023. 1923. 1823.L723. 1623.1523.7423.1323.t223.1123. 1023.0923.0823.O?',23.0623.0523.0423. 0323.0223.0123.0022.9922.9822.9722.9622.95

Feet.7829784L785378657876?88879007912792379357946?958796s798170928004801580278039805180638075808680988110812281348146'4 81588170818281 94

I

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Barometer I r-nlu"aHs.. ; Heights'l___

Inches.22.9422.9322 "9222.9722.9022.8s22 8822 8722.8622.8522.8422. [tB2? ,8222.8122.8022.7922.7822.7722.7622,7522.7422.7322.7222.7122.7022.6922.6822.6722.6622.6522,6422 63

Feet.820682188 :3082428254826682788390830283148326833883508362837483868398841084228434844684588470848284958507851985318543855585678579

101

Barometu. i

Readines. i

Heights.

Incbes.22.6222.6L22 .6022.592?. 5822.5722 5622 .5522.5422 .5322.5222 .5t92 5022 .4s22 .482a .4722 .4622.4522 .4422.4322.4222.4122.4022.3922.3822.3722.3622.3522.8422.3322.3222.81

Feet.85918603861 586278638865086618673868586978709 '

872t87338745875787698781879388068818883088428855,8867887988918904

8928894189538965

q

102

BaromqterBeadings.

Inches.22.3022.2s22.28y2 "2722 "2622.2522.2+22.23qq oDphJ . slkJ

22.2122.2022 7s22.7822.7722 1622.7522.L422.1322.L222.7L22.1022 .0922 .0822.0722 .0622.0522.0422.0322.0222.0132.0021 .99

I

Heights. I

----tFeet. I

89?? I

80e0 |

900290149026903990519063907590889100911391259138915091629t749187919992t2922+923692 r9926292749286929893119323933693489360

BarometerReadings.

Heishts.

Inches.21 .9821.9721 .9621 .9521.s421 .9321.92zl.gL21 .9021 .8921 .8821 .8',7

21 .8621 852L 8421 .832r.8221 .8121 .802l .792L.7821 .7721 .762L.752L.7421 .732L.722L.712L.7021 .6921 .6821 .67

Feet.937293849397941094229435944794609472948594979510952295359547956095729585959796r0962296359647966096729685969797109722973597479760

]Irl

ll

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103

i

BarometeriHeadings. Heigtrts.

I

Bar,',rneter /

Re'rdings. r

fnches.21.34O1 DDPr . q),,

?1.3221 3121.3021 .2921.282t .2721 2621 .25q1 qAru l.. ,tuT

21 .239.1 9..).dl.Pg

21 .:,!21 .202i.1921 1821 .7i21 1621.152t.1421 .1321 t227 7121 .1021 .0921 .0827.0721 .0621 .052L.042t .03

Ifeights.

Inches.21 .f,t)21.6521.6421 .6327 6227.6t2L.6021 .5921.5821 .5i21 .5621 5521 .5481 .5327 5227 itl21.502l .4921 .4827.4721 .462t.452t "4427.4:321, .4221 .4121 .4021 .3921 .3821.3721.3621 .35

Feet.977a978597979S10982298359818986198739836e89E

Peet.1017610189102021031410':281rJ:J41102531(J26610?78102911 0i10.{10:i1710:i3010:1431(i355i c3ri80}i1039 I040704?00432044ij045sa47l048 I0497

. 99] 1

9933933699499962997 499879999

1001210025100:lg10r,b0100631 00751 008810i011011410r26101391015110164

1050910522 .:i.

105351054810i617C574

!

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104

BarometerReadings. IIeights.

Inehes2L.A221 0121 003{). gg

20. 9820.9720 .9620.9520.9420.9320. 92

' 20.91'J0.90,)0.9920. 8820.8720, 8620. 8520. 8420.8320.82

i li 2C. 8120.8020.7s20. 7820 .7720.7620. ?520.7420.7320.7220.71

Feet.105871 060010613706271064010654106671068110694107071 072010733107461075970772107851079810811708241083?1 0850108631087610889109021091 5109281094110954109671098010993

BarometerRead rngs

Inches.20 .7020.6920.6820 .6720.6620 6520.6420.6320.6220. 6120.6020. 5920.5820.5720. 5620.5520.5420. 5320.5220.5120. ,50

24.4920 .4820.4720 4620 .4520.4420.4320.4220.4120.4020. 39

IIeights.

X'eet.110061101911032110451105811071110841109711110111231113617149111637tL76111907720471217112301I2437t2571L2707t284112971131177324113381135r1 136471377I 13917740411418

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Heights. Ba*omet., I rR.;;T;s;' Heigltts'

fnches.20.3820.3720 3620.3520.3420 .3320. 3P20. 3120. B020'2920.2820 2720.2620.2520.2420.2320.2220.21,20. 2020. 19

Feet.11431774M7745771470114831149611509115231153611550115637157711591116051L61811 6321 1645116591167311687

Inches.20. 1820.1720. 1620. 1520.7420. 1320.7220. 1120. 1020. 0920.0820.0720.0620.0520.0420.0320.0220.0120.00

Feet.11700117741L727LI74L1i754117681178111795118()811821118351185911863118771189111905119181193211945

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106

The followiog table is to be used

when applying the modified fcrmulaof chapter fI :

D-6oooo(rog B-ros ay(r+ Lffig)Rur,r.-Fincl in the table the loga-

rithms of the balometer reactrings tohundredths of an inch. SuJrtract these

logarithms and multiply the remainderby 60000. The prod.uct is the approx-imate clifference in altiturle betrveen thetrvo stations. To apply the correctionsfor temperature, add the temperatures

of the two stations and subtract 60".

Inerease the above approximate value by

sto of itself for each d egree of excess

above 60o. If the sum of the teripera-ture is less than 60' diminish the value

by a like amount.

Bar.IIeight.

I

Ir

r

F

LN

!-

I

k

220001020304050607080910111213741016771819202Li)o

2324252627282930

107

TABLE II.

Log. Bar. ..

Ileight. I LoS'

3 "31242.34262.3-1282.34301.3432r.3434t. 34361. 34380.34400.34420.'s4439.34459.34479.34498.34518.34537"34557.34577.34596.34616.34635.34655.3467434694

.34713

.34733

.34753

.34772

.34792

.34811

.34830

2281lJ2ODdr)34.)FOU

36.rl)OJ

3839404742434445464748,lg5051xc!OK)

5354OD

56D'(

58596061

3 .34350.:t4869.34889.34908.34928.34947.34967" 34986.35005.35025.35044.35064.35083.35102.35122.35141.35160.35180.35199.3521 8.35238.35257.35376.35295.35315.35334.35353.3537r*.35392.35471.35430

69707172l?f)to747576ll7B?980818283848586

88899091929394

. 3558335603

.35622

.35641

.35660356?9

.35698

.35777

.35736NFPF P.JOiOO

.35',774

.35?93

. 3581 3

.35832

.35851

. 35870

. 35889

.35908

.35927

. 35946

. 35965

.35984

. 3600336021

.36040

.36059

108

Bar.Ileight.

229596979899

230001020301050607080910117213741516t71B1920219.r.

2324252627

Log"

3 .36078.36097.36116.36135.36154.36173.36192.36211.3s22e.36248.36267.3638S.36:105.36324.3634236361

.36380

.36399

.36418

.36436

.36455

.36474

.36493

.36511

.36530

.36549

.36568

.36586

.36605

.36624

.36642

.36661

.36680

*lilirr-{j

$,A;'

dt

ti

I

Bar.Height.

I

23282g3031

a2DOdq)

343536c>fio/3839404142434445464748495051525354cc5657585960

3. .36698.36777.36?36. 36754.36773.36791. 36810.36829.36847. 36866.3r;884.36903.36922.3.6940.36959.36977.36996.37014.37033.37051.37070.37088.37107.37125.37744.37162.37181.37199" 37218.37236.37254.37273" 37291

2361626364oo66676B69707lryqaK)t?c)/i)

74'tD

76tl?B798081B283848586878B8990919293

3. it7310.3;328.37316.3736;.37383" 3740 r

"37420.37438.37457.37 475.37493.37511.37530. 8?548.37566.37585.37603.37621.37639.37658.37676.3769437772

" 37731.377 49.37767" 37785.37803.37822.37840.37959.37976.3?894

109

Log. Bar.IIeight. r,ug.

Bar.Height.

23s49596979899

240001020304050607080910117213l41516771819202l2223242526

110

Log.

3,37912.37931.37949.37967. 37985.38003.38021.38039.38057.38075.38093.38112.38130.38148.38166.38184.38202.38220.38238.38256.38274.38292.383t038328

. 383+6

.38364

.38382

.38399

.38417

.38435

. 38453

.38489

I

-P.ut' I Los.Height. I

l

-z4w i s .esbo;28 i .3852529 i .385433031o(tOKIOD!)?)

3435366l-FtOJ

3B3940414243444546,lt l+t484950515253

.38561

.38579

.38596. 3861 4. 38632.38650.38668.38686.38703.38721.38739.38757.387?5.38792.38810.38828.38846.38863.3888L.38899. 389 1?.38934.38952.389?0.38987.39005'"3902339041

.39058

.390?6

54cc56o'/5859

111

Bar.Eleigh t. Log. Bar. r

Height. l-.,cE'

2$A616?636.4

U.)

666?(jS

69?07tryolKrryoJr)

\4rj)76tl?87gB()

81R2

B3E4858687B8B9909192

2193949596979"q

992500

010203a4050601c8r)g10111.)

1314l.)167718192027Lq.HH

232425

3 .39672. 39690. 39707.39724.?,gi 42. i9759.'3977'7.39794.39811.39829.3t1846.:19863.39881.iiiig93. ::9915.39933.399;0.39967. 3998540003

.40019

.4008?

..{005.{

.4$071

.40088

.40106

.4012')

.40140

.4A1W

.4Ar75

.401s2

.40209

.4A226

il

il

:

E

LLz

V

ir

il.

Lor:.

3.40807.40e,24.40841.4{r858.40875.40892.40909.40926.4094,3.40960.40976.40993.41010.41027.4L044.41061.41078.4109ii.41111.41728.41L45.4Lt62.47179.41196.47212.41221).41248.41263.4"1.P90.4129641313

.41330

.41347

Bar.Height. Log.

25262728293031aoUKJo.)d')

343536.)tnOJ

38394A4t424ii4445464748495051525354O;t

565758

3.40243.40261.40278.40?95

,/AO!*-). €Jt)ap

40329.4A346.40364.40381.40398.4,,)415.4A4*2.40449.40466.40483.40500.4051.8.40535" 40552.40569.40586.40603. 40620.4affi7.40654.40671.40688.40705.40722'40739.4A756..10773.40790

Bar.Fleight.

2551)60616263646566676B69707772r,1.)JO

747576Fil.,lt7879BO

8182838485868788899091

i

:

I

Log.

259293s49596s79899

2600010203040506070809101172137415161718

,19202looPKJ

2324

3 .41364.4 I 380.41397,,4L4L4. 4143C47447

.4t464,

.41-{81

.4L4s7

.4151441531

.4154741584

.41581,4L597.4r_61441631416474166441 6814769747773

.41731,41747.41764477874L797

.418t4

.41831

.4t847

.418634188041896

262526r)rynl28293031OOe)&)a) 5)oo3435366' !.1OJ

3839404t424344+o464748495051525354bc56o't

3.4191:l.41 929. .{1946.-11963.11979.41996.42012.42029.42045.42A6242A78

.4209542111,1q1,)n

.'r^JLrJa

42744..4216042177

. 42193

.42210

.4222{i

.42243

.4225942275

.4:22924230842'"2542341

.42,35742374

.4ffi91)

.4240{j4242342439

26585960616363646566676869707L7211D,q)

747576l'ltj,a7B79808182838485868?8B8990

I 3 .42455.42472.42488.42504.42527.42537.42553.42570.42586

426424?6194:635

.42657

.42667

.42684

.42700

.42776

.42732"4274s" 42765.42"i8L.427s7,4281342830

.42846,428$242875

.42894

.12971

.42927

.42943

.42959

.42s75

LL4

949596979B99

2700010203a40506070809101112137415161718192021oopE)

23

.43040

.43056

.43072

.43088

.43104

.43120

.4313643152

.43169

.431 85

.4324L

.432171D;ID)

. tdri/Ur)

.43249

.43265

.43281

.43297

.43818

.43329

.43345

.4336r

.43377

.43iJ93

.4340s

.43425

.43441

.tb+sz

.43473

.43489

.43505

115

Bar.Height.

27242526ot1pt282930310nOKJo.)DO

3435366t11o/383940lt,4243444546474B495051525354DO

56

Log. Bar. , .rr.[t t. Log.

2i57585960616263646566676B697A71n,oa;)lJ.)I t-)

7+rO

76tt78798081828384UC

86878889

3.44A44.44059.41075.44}gt.44107.44L22.44138.44t54.4417 0.44185.4420L.44217.14232.44248. J,42{ii.442 .;9,{ t2g5

..14i1i14432t3

.44342

.44358

.44373

.44389

.444A4

.4442A

.44436

.44451

.44467

.4448A

.444s9

.44514

.44529

.44545

Bar.Height.

27s0919293949596979899

280001020304050607080910117213t41516t71819202122

116

Log.

3.44560,44576.44592.44607.44623.44638.44654.44669.44685' .44700.44llti.M731.M747.M762.44778.44793.44809.44824.44840.44855.44871.44886.44902.M917.44932.44948.44963.44979.44ss4.45010.45025.45040.45056

Bar.Height.

2823242526272B29BO

313233343536373839404l42434445464748495051525354bc

Log.

3.4507t.45086.45L02.451L7.45133.45148.45163.45179.45194.45209.45225.45240.45255.4527L"45287.45301.453L7.45332.45347.45362.453?8.45393.45408.45423.4543s.45454.45469.45484

.- .45500* .4bb1b.45530.45545.45561

117

IBar. I log.Height. I

t--2856 I S.455?6

57 | .4559158 i 4560659 .4562160 i .4563761 .4565262 4566763 l .4568264 I 4569865 I .4571266 I . 45728

Log.

876869707172t't,-,e)

.45743

.45758

.45773

.45788

.45803

.458i8

.45834

.45879

.45894

.45909

.45924

.45939

.45954

.45969

.45984

.46C00

.46015

.4603C

.4604546060

28899091g2

93949596979899

2e0001020301iJi;

0607080910117213t41516t71819202L

3 .46075.46090..16105.46120.46135.46150.46165.46180.46195.46210.46225.46240.4627t0. tg?rlc.46285.46300. t6315.46330.16344.46359.46374.46389.46404.46419.46434.46449.46464.46479.46494..46509.46523.46539.46558

74 .4584975 " 458e,17677;8i98081B2838485868?88

118

Bar" i

Ileight. I

Log' Bar.Hr-*2955

565'l5B596061626,3

64n>oo666768697071t1c,,L)tlDad

74'(b

76r\nal7B7eBO

B18283B485863?

2s22 I a.4656823 I .4658324 i .46beg25 i .466132627289Cl

3()otOIQ')oK)oot)e,

343536f,-F/OJ

38tu9

4047424344454647484e5051525354

"":_3.47056

.47070- 4?085.4710tt.47174.47729.47L+4.47159.47776.4?188.472A2.472t747232

.47246",L72Et.47276.47290.47305.47319.47354.1734s. 4? 36:i.4?s78" 47392.47407.47422.47436.47451

"* .47 465.47480.47494.47509,"+'tszt

.466 )7

.4$6,+2" 46657.46672.46687.'+6i02.46716+6731

. 467 4646761

.46776

.4679046805

.46820

.4683546849

. ,46364

. 46879

.468944{i9094692346938

.46953

.4696746982

.46997

.47072

.47026

.47041

Bar.FIeight.

2988B990919293949596979899

30u001OJ030405060708091011721314151677181920

*

119

Log.

3 .48015.48030.48044. 18058.48073.48087.48101. 481 16.48130"48744.48159.48173" 48187.18202.48?16.48230. ,18144

..182i1948273

..1828?

. 43302

. 4831 6

. 48330

.48344

.4S:150

.48373

.48387

.4840:484164843CI48444

.49459

.48473

Log. Bar.Height.

3 475.28.47 55:)

/*-/1-t4rDUt4758347 5964i 6LL47625

,47640.4i654.47669.47683.47698.47772.47727,177 4l477554777 A477844779s47813,+7828

4784247857

.478i1

.47886

.47900479L4

.47929

.17943

.47958

.479724798648001

302122tartJ

2425262728293031oooK)oooo343536oPr)I38394041lo

: /i,'

,13

44454647484950515253

12U

Bar.Heiuirt.

3054oj)i)uDI58596061626il6'l6566676869707172IJDad

747576tt

Log Bar.Height. Log.

3.48487.48501.48515.48530.48544.48558.48572.48586.48601.4861548629

.486-1348657

.48671

.48686

.48700

.48774

.48728

.48742

.48756

.48770

.48785

.48799

.48813

307879BO

81B283B48586B78B899091og

93949596979899

3100

3.48827.48841. 48855.488694888348897489114892648e40

.48954

.4896848982

.48996

.49010

.49A2449038

. 490524906649080

.4s094

.49108

.49122

.49136

t

t

I!t

i

i

tt

I

t

t

t

t

I

l

l

l

t

t

t

t

I

t

I

t

tt

tlt

L

Lz]-

TABLI TII.BAROMETBIC READI\GS I\ ]IILLI}IE

ALTITTDES I\ ]IETERS.

This is from RrrclAu's tirble. The fortlrr.tJa

for calculation of cliffereuce of altitucle of two

stations i-* D -'/,-/r't 11-- 2'l-:-l t

' \ ^ iloo I itr s' hicir t)

is tlrc differencc ui htigilt iu ntetet's, /t, anrl //are barometer retciinss in rnillimetcrs and I ancl

t' aretire ternpet'&tul'es iu centigrzrCe clegrees.

I

Miil. i }Ieters.__l_500 i sgos. +501 3349 ..+

]lcterr.

,502 i 3333 5503 I 3317 6504 i 3301 7505 32E5 0506 3270,150? i 3254.3508 i 3238.5509 i 3222.8510 I 3207 1

511 | 3191.55L2 i 31.75.9513 I 3160.35L4 i 3744.7515 t 3729.2

3ig(-). tr?;6D 3l?io. +

".'73;.62720.927()6.12691 .4267{i. 8

I Z00Z.f| ?647 .5i 26.32. I

2618 326DJ . 895Bg ..;2574 I2560" 32545 I2531 .5251?. l

516 I 3113.7 i

518 i So8?.8 I

I

I

I

D{ir. I

!!E I

D0't I

558 I

5.-;9 I

560 I

.561 i

562 I

563 i

Dt-l r

568569570571572F F.)iJto574.575i)io5775?B579580581582583584585586587588589590

2360 62346 52332 52318 4%a4 4229A 42276.52262 62248 72234 82220.92207 .72193. 32779,52165.72152.02138. 32724.td2110.92097 .32083. ?2070. 1

2056.52042.9

5915925935945955965975985996006016026036046056066076086096106116t2613674615616617618619620621,622623624

I

I

Meters. iI

__lI

2502.7 i

2488.4 i

2474 7 I

245e.8 i

2445.6 I

2437 42477 2

56.4 | e+Oa.O565 I 2388. B

566 | Zg7+.7

II

Mill. I M.t....'__2029 42015 I2A02 4989.0975.5962 1s48.7935 .4922 .0908. 7895.4882. 1

868. B

855.6842.4829 .2816.0

1802.91789.8777 ti .71763.61750.51737. 57724.47711.41698. 51685.57672.61659. 71646.81633.91621.01 608. 21 595 .4

Mill.

62562662762862963063163263363463563663763863964064164264364464Ir64664764864965065165265365465&65600'/658

Meters.

1582.61569.81557.17544.41531.7151 9.01506.37493.71481 . 01468 .41455 , 81443.37430.71478 .21405 .71393.21380.71368.:l1 355.81343 .41331 .01318.71306.37294.07281 .77269.41257 .11244.81232.61220 .41208 21196.0I183.87t71 7

L23

;;i;;ffi.,.-ffi__l_lll6.sr-illbe-l ji Gr'3-i=?s -?.? -B?rr6to I tt+z.+ ll og+061i1135.3iCg;662 j rrze.s ; ago66iii1111 3 69;6$,+ i1099.! 6956fi5 I 10*?.3 69966{ii10;5t ?0u667I1Ce3? 7016u8 1(i;1 J ?02669,L0393 ?0367u 1027. 3 70467t i 10154 I zos612 i 1003. 5673 i gg1 .',7

674 I 979.9 ,',lUg6751 968.0, ?U1^,

676 I 956.1677 I 941.3678 i 932.6679 i 920 8680 I 909 0681 I 897 3682 I 885 .6683 I 873. e6841 8622 ?i8685 I 850.5 71e686 I 838.0 730687 I 82 7.3688 I 815.6 722689 I 8C4.0 i 723690 | 7s2 .5 t' 7246sL | 780.9 i 725892 i ?69. 3 t' 726

t24

Mill, Meters.

76f i' 10.57621 00763 , -10 5764 -2A I765 -31 4?66

" -47 8767 | --52 .2

73. 083.4937

-fi4 1

-r74 4

-734.7

M

76s770777772DI'IDa la)

774

't'l D

776ll I

778

i

ill. I Meters.

L25

In comparing tire Aneroid with a MercurialBarometer, correc[ the ]atter by the followingtable, subtractin g tbe correeti on-s.

TABLE IY.

Reduction of Jlercurial C'olumn to 3?' Fahr.

Brass scale to l,aroiii,:iei' tr)Tract at 62' Fahr.

Terap. 30" 25"

32

.iO

40

45

50

oo

6C

6,5

70

io

80

85

90

95

100

. L)t )[f

l-r1 -rvl- i

tr31

0+1

05s

071

081

098

.111

125

.138

.151

.161

,178

.191

.008

.015

026

. 0:17

. t){s

. ()ig

.0?0

0s2

093

.104

.115

.126

.137

.149

.159

.006

.012

.021

. 030

038

.047

.056

.065

.a74

.083

.092

.101

.11O"

. 118

, L'd'l

h

12 ri

TABLtr Y.

BARoME'ITTICPRESSURESCORRESF0NDINGToBOILING \YATER TEI\IPERATURIIS"

Tenttrs bT c'ac h f) egree.

z1 -a-l

--.6- , - It

Whole Deg. i

--a-"0 -iiinlinlinlitt.iin'

183 ; 1$tlZ i rO 389 I 16.461 I r0 See I 16.605is+ rri ii u to ?,-rP l(i 826 1u.{}00 16 974

i#,ii ti4E 7i 133'1;1u7 11 272 17.848isa i; etu tt ,tgu t? i;5 17 052 17 ?Pg

ie? , rt S00 : 1? u8ll 1;.9G1 ' 18 0r;-e 18'- l?iBB iB isi 1 78.274 ts 353 1 ts"+az l ts starae i rii irez I 18 6?2 , 18 ',i?q i 1a 9q? i H 914ieg,rs n9P l1B 6?2 18 'i53 i18 833 18 914

igo iiB 996 i19.0'7? , ttl.tl-rtl I1e ?41 I 19.324iei iS ;oi i le 4eo 1e 5?:r t le fi5? lt) '741

igz ; tg B2b I 19.910 19 995 ; 2i).080 I ?0.16tiig3 Izo zst |20 33E i :'lg +24 iit; 511 :10 5et

is4 i g0 oss i zo 773 i, 20 861 i D0 1i4e r ?1 OqB19.tr:20 685 120 775 ; :r(.l.titil '"r,u :r'lr' 3r u'iuie; ; il .1i6 i zi zro ; 21 :!o; 21 ::35 ,1 .485

ie6 i zl dns i zr 066 j 2t ?5s ' p1 . b4e i !1. e41

lgi zi 03:i 2? 1t5 i 21.218 22 ;i11 i *:l 404

19U Y'a 4Ud I Zl itil4 i z< . oou i .P ' t(JJ- I

i99 zt gT1 I pB 0o? : P8.163 | 23.259 r 23.356iort 2r.Adg',zg bbo:J:1 .tl48 I:3.i''lti i23.845itri Jri e{B i 24 t)42 24.742 iz+ z+1 124.341,

tql ,':4 *ti?!.i!? ?! 9!+ I 3t ilg l71- 9Il

Itrl /;d tiO;) I -Lr/ I,tJP'?J:: I

iga z'z 4sB i z? h92 i 2? 686 i 22. ?81 | 22.876i99 zt gT1 I pB 0o? : P8.163 | 23.259 r 23.356iu,r 2t Ads &s bqq , 'i?

q4Q i :q i+9 i 3? Pt?

zos t4 t)-19 i25 051 25.154 i2:> 257 125 361

20.1 ),J {65 i 25 569 I 25 67 4 I 25 779 I 25 q84

zos 3;i 3l)0 i 26 0t)6 i 26.202 i 26 309 |26 416

zoo 2{i 523 i 26 631 i 26 .740 i 26. 848 I ?6 95?207 27 066 i 27 ,t76 | 22.286 127 .3s7 127.50?zos ,

p? 618 i 27 .730 | 27 q12 l?7 2l+ I ?q 9I?zog zs 180 i 28 3e3 i 28.407 | 28.521 i 28.636zro zs ;51 I 23 866 i 28 e82 i ?q gqq i ?q ?1?itl ' z,t ffi1 I zs .44s I zg s00 I 29 684 i 2e 803

2r2 rlr . e33 I 3c 0,+L' 30.191_30,!_81_i9_191

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