traverse survey of the white nile

7/29/2019 Traverse Survey of the White Nile

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Notes to Accompany a Traverse Survey of the White Nile, from Khartum to Rigaf, 1874Author(s): C. M. Watson and Richard StrachanSource: Journal of the Royal Geographical Society of London, Vol. 46 (1876), pp. 412-427Published by: Blackwell Publishing on behalf of The Royal Geographical Society (with the Institute ofBritish Geographers)

Stable URL: http://www.jstor.org/stable/1798682Accessed: 20/10/2010 19:04

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412 Lieut. NVATSON'SNtotesn a Traverse urvey12 Lieut. NVATSON'SNtotesn a Traverse urveydull samenessof straggling roots,mud,and dead greenmassesof foliage. The populationconsistsonly of scattered fishilag-villages,with theirlittle patchesof landgrowingmaize,bananas,plaintains,coco-nuts, nd peppers; and we should not estimatethem at morethan1000 souls n the wholedistanceof 100 miles.The channelwouldbe available orarlysteamersof about 5 feetdraughtof water.From Bonny to New Calabarthe channel is constantlychanging, alld the banlvs abound with quiclQsands; ut forvessels of largersize, and not over 10 feet draught, here is agoodpassageoutsideBreakerIsland.

The RiverNew Calabar,romthe shipping o theoil-malkets,affordsa fine safe channel for vessels of fully 10 feet draught.After passing ElvaSa,mrhichs some45 to 50 miles from themouth of the river,the country mprovesvery much,the man-groveceases,and moderatelyhigh land,well wooded, peaks ofgreat capabilityforany tropicgrowth.At AmaSa,say about25 miles distantfromEwafEa, e foundthe countryvery good, and about 15 to 20 feet above high-watermark. It is evident,froln the profusegrowthof every-thing, that the soil mustbe virginin its richness. The nativesseenl poor and indolent,and are inclined to be troublesome.We thinlcthe povertyof appearancearises fromthe incessantquarrelling betsveentribe and tribe, as they are constantlyplunderingand capturingeach other,the captivesbeingalwayssold to slavery. ln physiquewe think they are inferior o themen at the mouthsof the rivers.

XVII. Notes to clecompany TraverseS?6rvey f the WAtteNtle, rosew hc6rtql,rewoRigaf. By Lieut.C.M.WATSON,.E.THEourneyfrom Cairo to Shartum,and up the White Nileto Gondokoro,s nowso well knownandhas beenso frequentlyand fully described, hat it will be sufficientto make a veryfew remarkson the routewhichwas followedon the occasionthat the traverse survey of the river,which accompanies hispaper, vasmade.Havingreceived nstructions o join GolonelGordon,C.B.,OT1the Upper Nile, I left Suez, in company with LieutenantChippendall,R.E., nthe 31stAugust, 1874,and xvereaclledSllakimon the 5th September.Leaving Suakimon the 11th of the samemonth, we arrivedat Berberupon the Wileon the 24th. The route++e ollo^ed

dull samenessof straggling roots,mud,and dead greenmassesof foliage. The populationconsistsonly of scattered fishilag-villages,with theirlittle patchesof landgrowingmaize,bananas,plaintains,coco-nuts, nd peppers; and we should not estimatethem at morethan1000 souls n the wholedistanceof 100 miles.The channelwouldbe available orarlysteamersof about 5 feetdraughtof water.From Bonny to New Calabarthe channel is constantlychanging, alld the banlvs abound with quiclQsands; ut forvessels of largersize, and not over 10 feet draught, here is agoodpassageoutsideBreakerIsland.The RiverNew Calabar,romthe shipping o theoil-malkets,affordsa fine safe channel for vessels of fully 10 feet draught.After passing ElvaSa,mrhichs some45 to 50 miles from themouth of the river,the country mprovesvery much,the man-groveceases,and moderatelyhigh land,well wooded, peaks ofgreat capabilityforany tropicgrowth.At AmaSa,say about25 miles distantfromEwafEa, e foundthe countryvery good, and about 15 to 20 feet above high-watermark. It is evident,froln the profusegrowthof every-thing, that the soil mustbe virginin its richness. The nativesseenl poor and indolent,and are inclined to be troublesome.We thinlcthe povertyof appearancearises fromthe incessantquarrelling betsveentribe and tribe, as they are constantlyplunderingand capturingeach other,the captivesbeingalwayssold to slavery. ln physiquewe think they are inferior o themen at the mouthsof the rivers.

XVII. Notes to clecompany TraverseS?6rvey f the WAtteNtle, rosew hc6rtql,rewoRigaf. By Lieut.C.M.WATSON,.E.THEourneyfrom Cairo to Shartum,and up the White Nileto Gondokoro,s nowso well knownandhas beenso frequentlyand fully described, hat it will be sufficientto make a veryfew remarkson the routewhichwas followedon the occasionthat the traverse survey of the river,which accompanies hispaper, vasmade.Havingreceived nstructions o join GolonelGordon,C.B.,OT1the Upper Nile, I left Suez, in company with LieutenantChippendall,R.E., nthe 31stAugust, 1874,and xvereaclledSllakimon the 5th September.Leaving Suakimon the 11th of the samemonth, we arrivedat Berberupon the Wileon the 24th. The route++e ollo^ed


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8miltewfOhf tUsmd

of the Ceveredw^vood *tWH I T EroN I Iro7onghe5wl!terXby- Iieut! Watsou& ChippendAll..E.

1M: 1 f 8 20 3nAlidL 3111tD loz trour coverd wSeGeo4r7tictil Miles I E765't:fi?E7

Water charI 2-eX. ...7trdser ha7ui 1+ rnile .".ia o Wato a great dvtsta7z.ce-.3,,/

llistzat desert vtsiblS-tt . 4^ t1-Deserr p pro ? n >#>ffiNa,

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Positions ietermirLed astronolnicaZly.:D1:a2;.Fashflda 9? 5h' 16 "

Sobat 9?23' fjO"Shambeh 7? 5' 59"Ca7LEsseS 6?4d' 23"Bohr 6?1S' 41"Gordo7uro 4?54' 28/'RigaS 4? 44' 32 "

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?ffi? bai Woode


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413f the WhitcNile from K11artumo Riyaf.wasnot thatwhich s usually akenby tlle merchants aravalls,and ed over steeperandmore ruggedmountain-passes.l'hisroute has the advantage f being Bell suppliedwith water,which s foundon each day's march, nd s generally f gOodquality. The distance romSuakim o Berberby this road sabout270 miles.For the greaterpartof the wav, t leads overrangesof hillsof solcanicorigin,andacross evel tractswhichhave evidentlybeen the cratersof long-e:xtinctolcanoes. These are of anirregularlyilcular orm, nd omeare12 or 15 milesacross, ndsurrounded ith steep, black cliSs. The surface s for themostpartcoveredwith sufScient oil to allowof the growth fa considerablemotlntof vegetation,and water s generallyfoundby digging. Every now and then lleapsof lava an(-lscorine re passed,andtrapdylies stand high abovethe sur-roundingevel.The highestpassnhich xYerossedvas athermore han300Gfeet abo-ethe sea.Parts of this collntryale very beautifu],nd wouldappearto possessgreat capabilities f improvement,f arrangementswere made for preservinghe waterwhich alls during therainy eason.After a felvdays'delayat :13erber,e proceeded y steamerup the Nile to Khartum. The riverwas nearlyat its greatestheight, and navigationwas consequently asy even at thecataracts hich ie between hendy ndKhartum.At this pointthe Nile passes hrough rangeof hills which ontractts bed,and so increase he rapidityof the current. Whenthe Wileis lo+s, t is not possible o pass hese rapidsexcept n boatsofvery ight draught, s thereare manydangerousunken ocks.The distancefrom Berber o Khartum ccupied ix daysSbut it canbe done n from hree o fourwithout ifficulty.We remained few days at Shartum,and then proceededby steamer p the WhiteNile to Gondokoro,nd reachedt inthirty-four ays. It wason this journey hattlle acconlpanyingsketchof the riverwasmade.It may be interesting o explain he manner n whichthetraversewas aid down.A 4-inchprismatic ompasswas placed n that part of thesteamer here it wasfound o be least aSectedby the iron ofthe vessel, and a readingwas taken at each alteration f thecourse f the steamer. Theactual imeon eachcoursevasalsonoted.As the variation f this compass, f course, iffered onsider-ably as the directionof the head of the vessel altered,ob-servations ere aken as opportuniti oSered o ascertainhe


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414 Lieut.NVATSON'S!Gotesna Traverseurveyactnalvariationorrespondingo each course,anda tableofvariations asconstructed.Tlletraversewasplotteddaybyday in a log-bookimilarnformto thatproposedy Mr.Galton ll his ' Art of Travel,'and all observationsndnoteswerekept in the samebool.Theforms e:xcellent,ndmostconvenientn everywav.As the rateof the steamerwasnot knownat starting,hecourseswereplottedona time-sca]e, quarterf anhourbeiIlgrepresentedy the fifthof an illch; andthiswasadheredo asbeingconvenient,ven after he rate ofthe steamerhadbeenfrequentlyascertained.It was afterwardsound that thescaleadopted Tas earlyequivalento 5 geographicalmilesto tlle inch.A little difficultvwasat firstexperiencedn ascertainingwhilein motion, he veloeitfr f the stream, ndthe rate ofthe steamer. A patent og gaxTensatisfactoryesults,as itegisteredherateat avhichhevesselwaspassint,hroughhewater,and thiswasequivalento the actualrateof progressaddedto tlaevelocityof the current. It was,besides, o fre-quently toppedn its revolutionsy floatingegetablematteras to be practicallyseless. The followingmethodwas there-foreadopted,nd s noticed, sothersmayfind t useful.The steamerwasprovidedwith ronstanchions,et into eachbulwark,sawning upports.rThesetallchions erein pairs,oneof each pairon the portbulwarlc,nd the otheron thestarboard,nd the line joiningeachtwowasexactlyat rightangles to the centre line of the vessel. Twopairsof thesestanchionswere selected,one pairforrardand one pairaft,andthedistance etxveenhsemccuratelyleasured.Assuminghat thevesselwasmovingahead,andit was de-sired o ascertain er rateof speed, tree or other isedobjectonthebankof theriverwaschosell, lldthe exact time,to asecond,at whichthe line joiIling he tro forwardtanchionspassedt wasnoted,andalsothe tilneat wllichhe linejoiningthe twoafterstanchionsassedllesameobject. ThediSerencebetweenhetimesbeinbknown, nfl alsothedistance etweenthestanchions,t is evident hat the rateof thevesselcan beascertainedy a sileplecomputation. t is, in fact,a reversalofthewell-knournethod ywhichhe rateofa stealuersfoundona measuredmile.To save rouble, tablewasconstructedhichgave the rateof thevessel n knotsper hourcorrespondingo eac:E umberof secondswhichelapsedafterthe forwardtancllion-lineadpassed ny object ntil heafterine hadpassedhe sameobject.It is evidentthatthe samemethodwasapplioableor ascer-tainingthe rate of the currellt,by observillg mallfloating


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of the WAziteile from Khartuano Rigaf. 415objects n the stream;numerousbservationsf this kindweremade,and he meanresults ecorded.The notesandremarkswhichareenteredn the map,on eachside of the river,are taken llearl) verbatim rom the log-Wook,n which verything f interestwasrecorded n the spo.Astronomicalbservations eretaken at various tations romFashoda o Rigaf. An8-inch extant, eading o 10",wastheinstrument sed. Mthenevert waspracticable,tarsnorthandsouthof the zenith for latitude,and starseast and west fortime, were observed. Six readings, t least, were generallytaken. Lunarobservations eremade at Rigaf and Gondo-koro,and the relative lollgitudes f the other stationsweretakenwith a chronometerf sllich the rate was foundto bei:airlyregular. Theseobselvations re all appended o this?aper. A11 pportunitylso oSered or observing he transitof Venus n the 9thDecember, 874,andthe timesof contactof the planetat egresswere notedas accurately s the instru-mentsat ourdisposalwould llow.Meteorologicalbservationserealsotakendaily. The ane-roidbarometers sedwerecheckedat intervalsby comparisonxvithCaptainGeorge'smercurial arometers.Thesebarometersare filledwith great ease,and standveryrougllusagewithout

rn * . .suIIerlng ln,lury.The channelbywhichwe passed hroughhe luarsh-districtof the White Nile is the one formerlysed, ometimes nownas the Bahr-el-Gebal.The grass-barrier,hich made it im-passableor so lnanyyears,was cut through arly n 1874,andthechannels nownavigablewitholltheleast difficulty,houghthe width of openwater s very small in some places. rTheBahr-el-Zeraf,n the contrary, hroughwhich Sir SamuelBaker passedon his last journey o Gondokoro,s nowsaidto be blockedup. It is probable that the directionsofthe channels hrough his mass of vegetation re constantlychanging.The greatmarshmaybe said to end at Sllambeh, r aboutnorthat. 7?. From his point o Gondokorohe banksof thesriverare, for the mostpart,tolerably irmground. In someplaces he riverbreaksup intoa number f diXerenthannels,as will be seenonreferenceo the map.

At one place,betweenBohrandGondokoro,here s a largebranchof the river,nearlyas wide as the main branch tself,whichflowsaxvay n a direction o the east of north. TheArabs ay that t joinsthe River Sobat. This is a most inte-restingquestion, nd t is hoped hat it willbe investigated.We arrivedat Gondokoron the 14th November, ndwenton to Rigaf on the 29thof the samemonth. At that tirne he


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41(S Lieut. WATSONESotesona TrarSerseurreyof t1uewindbeganto blowsteadily romthe slorthaild north-east.Sickness lsoappearedo increase t tllesame ime.3Iaynotthis be dueto the fact thatthewind,passingos-erthe greatmarshes ich lie to the northN-ard,ndwhicharedryingup at this season,becomes hargedwithmalaria, ndcarriest to the comparativelyealthycountryn the vicinityof Rigaf?Thereis nowno Egyptia:nGoverllmenttativaat Gondo-koro. Thehead-quartersf theprovincereat Lardo.By themiddleof NovemberheNile hadfallenabout3 feetbelow hehighestpoirlt f thatseason,nd t continuedo falsteadilyuntil the endof January,875,+when left Rigaftoretulmo Cairo. Forthisreasonhe navigation assomewhatmorentricatehanwhenweascendedn November;buttherewasnoreal difficulty,ndwereachedS:hartumn sisteendaysafter eavingLardo. In manyplaces he fall of theriverhadquitechangedhecharacterf the country,nddistrictswhiclhad been completely nderwaterwere lOW dryandcoveredwithvegetation.AstheNilewasso low, hatit wasnotpossibleora steamerto get overthe cataracts etweenKhartum nd Shendy,weprooeeded y calnelto Berber,passing hroughMeroe, heancient apitalof Ethiopia, ndcrossingheAtbara,whichhadnowbecome n insignificanttream, otmore hanankle-deep.FromBerberwecontinuedo followheroadontherightbankof the Wileto Aboo lIamed,and thenceaclossthe NubianDesert o :@oroskontheLowerNile.The routefromWhartumo :Soroskos an interestingne.Thejourneyookthreeweeks,ncludinghaltsat BerberandAbooHamed. Of thistimesis anda half dayswere pent ncrossinghegreatSubiandesert.Thisroute romKhartumo Cairos the oneusuallyollowedbythe merchants,lthought occupiesmore imethan hatbySuakim ndtheRedSea.


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From tile resultscontained n the precedinOl'ablehe followingTable wasformed:- TABLEI.-GONCLEDEDATITUDES.| t Number ofXame of Place. Latitude North. separateg 0 Determinations.

O , ,,Fashoda ....... . .. .. 9 55 16 1Shambeh ...... . .. .. 7 5 59 2Canisseh ....... . .. .. 6 46 23 1Gondokoro . .. .. 1 4 ,?iA28 4

p Rigaf .. ....... . .. | 4 44 32 . 8_ .VOL.XLVI. 2 E

White MilefromKhartum o Rigaf. 417AP PE N D I X.

Besults of the Astronomtccl,lbservattons ade by LieutenantNYATSON,.E., t po8ttt0nS on theRiverNiZedxring the year1874. CalculatedbyWILLIAMLLIS, .R.A.S.,f the RoyctlObservatorySreenweh.TABLE. RESULTSFTEEOBSERVATIONSORLATITUDESYCIRCUMERIDIANLTITUDES.Date. Name of Place. Object. |1874. 1 1Oct. 23 YFashoda .. .. a ayfflni ..,, 25 j Sobat .. .. a aygni .. ::

Nov. 3 Shambeh a Gruis,, S ,, . .. Fomalhaut ..x ? 11 Bohr ....... .. Slm . .. ..,, 23 Gondokoro ....... a assiopeiae,, 23 | ,, .. a Eridani ........ .,, 27 ,, .. Capella ........ .,, 27 ,, .. Canopus ........ .llec. 4 Rigaf .. .. a aassiopeise ..,, 5 1 ,, .. .. a aassiopeise ..,, 6 ,, .. .. a aassiopeia,, 6 : ,, .. .. a Eridani ..... ..,, 10 , .. .. a CaSsiopeiae .,, 10 ,, .. .. a Eridani ........ .

| Whether | Separate ResultingN. or S. Obser- LatitudeFof 7enith. +-ation. North.N. 8 9 55 ;dN. 8 9 23 121iT n Cb )A OQU 24 267 5 587 6 06 46 236 12 414 54 15

4 54 37+ 54 64 54 524 44 14 44 414 44 404 44 564 44 16+ 44 45444 134 44 42

N.s.cs.s. Z,

I.N.

o. IN.CSo. [N. s.N. AS-N. WS. IN.S. j

8

66688S668X88


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Illterval in Days Resulting llifference ofbetween LoIIgitude.Names of Places. Obser^ations __ __for time atthe TwoPlaces. II1 Time. In Arc.

SobatXwest of Fashoda ..................... .. .. 2 2 34 l 8 38 31Shambeh, trest of E;obat ..................... .. .. S 3 20*3 0 50 4Canisseh, east of ShamlJeh .. .. .. 4 1 22*8 0 20 42Bohr east of Canisseh ..................... .. .. aI 1 50 1 0 27 31Gondokoro, east of Bohr ..................... .. .. (; 0 20-1 0 5 1Rigaf, west of Gondokora ..................... . .. 7 0 17 5 0 4 22

418 Lieut. NVATSON'S!Cotes7a Traverse urveyof theTABLEII. (::EIRONOMETRrCIFFERENCESFLONGITUDE.

(These resultsdependon the rate of one chronometernly.)

TABLEV.-RESULTSOFTHEOBSERVATIONSLUNARDISTANCES.B0RLONGITUDEY(The tabulardi3tances iven in the ' NauticalAlmanac have been aortected orGeeeerwoirehoObhe tilace) of the moorland Saturn as determined rom the

Date. Name of Place.

187s,Nov. 27 Gondolioro ..27}, ., 0.Dec. 15 Rigaf .. .., 15 ,, *-,, 15 , .. ..,, 16 , **

, 16 > *' ''

, 19 Xs .. ..

,, 16 , .. ...

Whether theMoon wasEast or West.

E.TV..W.W.E.E.T!.W.W.

t W

Number Resu}tingof LongitudeMeasures. East.

3 31 l5 453 30 59 0ti 31 38 455 32 1l 30:; 32 11 303 32 13 05 31 59 305 31 Sg 305 32 0 05 1 32 1 455 , 3t 46 30

Objeet o whichMoonwas referred.

AldebaranRegulus . .Saturn ..Aldebarana Arietis *.Saturn ..Saturn . *Saturn , .AldebaranAldebaranAldebara

From the results contained rx he precedinaTable the followingTable was.formed;-


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TABLEV. SEPARATEAILYRESULTS ORLONGITEDEROM UNARDISTANCES.

Resulting Longitude or Moon.Date. Name of Place. ConcludedEast of Object. T West of Object.

1874. ?Nov. 27 Gondokoro...... . 31 1.5 i5 30 59 0 31 7 23Dec. 15 Rigaf .. .. .. 31 38 45 32 11 30 31 55 8

,, 16 ,, .. .. .. 32 4 0 31 56 5 1 32 0 2I

In the precedingTable thereappearsone result for Gondokoro nd two forRigaf. But, by the chronometric ifference f lonaitudebetweenGondokoroand Rigaf contained n TableIII., the one result obtainedat Gondokoromaybe reduced o Rigaf, and the lonCitudeof Rigaf, as fundamentalpoint, thusdetermined s follows:-1874.

O * ,,Nov. 27 Longitudeof Gondokoro .................. .. .. .. .. 31 7 23 E.By Table III. Rigaffflest f Gondokoro. ....... . 0 4 22

,, 27 Inferred ongitudeof Rigaf .. .. .. .. .. 31 3 1 E.Dec. 1B Longitude f Rigaf .. .. .. .. .. .. .. 31 55 8 E.

,, 16 ,, 7 o ....... .. .. .. ,. .. .. 32 0 2 E.Fromwhich s adapted orthe absolute ongitudeof Rigaf, 31?39' 24"E.(meanof the threeresults).

With the adopted ongitudeof Rifflaf, 1? 39t 24N'E.,and the chronometricdiSerencesof lonaitude contailled in Table III., the lonaitudes of all theplaces included n that Table may now be deduced; and,adding thereto thelatitudes from Table II., the followinfflesults are obtained:-TABLE I. CONCLIJDEDATITUDESNDLONGITEDES.

Name of Place. Latitude yorth fLongGitude.ash, ,, o h #Fashoda .. .. .. .. 9 55 16 32 19 7Sobat .. .. .. .. 9 23 50 31 40 36

Shambeh .. .. .. .. 7 5 59 30 50 32Canisseh .. .. .. .. 6 46 23 31 11 14Gondokoro .. .. .. 4 54 28 31 43 46

2 E 2

WhiteNile romKhartumo Rigaf. 419


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420 Lieut.WATSON'Soteson a Tl averseSurve?/ f theTABLEVII. OBSERVATION-SFTHEEGRESS FTEEPLANETENUSPROM HESUN,IN THETRANSIT F VENUSACROSSHESUN,

DECEMBER 8, 1874.(Place of observation, Rigaf, latitude N. 4? 44' 32", lonitude E. 31? 39t 24 tXasalready detersnined. SeeTable VI.)

lSratch fast ofPhase ol)served. Watch Time. Rigaf Mean R.lgaf Mean Solar Tlme.Solar Time. (AStronomical Reckoning.)H. , ,, H., ,, H. , ,8Fomationofblackline Dec. S 20 35 26-0 0 27 19-6 Dec. 8 20 8 6-4

Xnimalcontact* ..............., 20 35 55 5 1 (:)27 19-6 ,, ' 20 8 35-9:ernal contact t ............... ,, 21 4 52*0 0 27 20-0 ,, 20 37 32-0

* Was a good observation.t It was diflicult to observe this lvith acouraey.


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These heights haare een calculated iom observationsmade with mercurialbarometers f CaptainGeorge'spattern for traveller3. The original observa-tions are stated to have been corrected or instrumental errors. \NTherenumber of observationshave been made in the same month, the means ofthem have been used as the data for the upper station. The barometricalobservationshave been reduced o temperature 2?, by the table for gradua-tions on glass scales, these barometers eing dividedon the tubes themselves.'l'he air temperatures ave been taken as correct. The followingare the dataused for the sea-level: the pressure having been obtained from Buchan'sisobarometricharts, and the temperature rom Dove's sothermal harts:-

Month | Pressure. | Temperature.Inches.February .......... 29-9 81*

June ... .. .. 29-8 82July ... .. .. 29SS 81Septenlber .......... 29 8 81October.. .. .. 29*9 80Noarember .......... 29 9 79

t December .. .. 29 9 78

WhiteNile fromKhartumo Rigaf. 421Reporton the Calculationsf Reights

Lieutenant WATSON,.E., on theSTRACHAN,eteorologicalOfficer.from Observationsmade byWhite Nile. By RICHARD

Elevation aboveSea Level.ate. Place.

1874Oct. 9, 10

Oct. 26, 27, 281875.

Feb. 61874.

Nov. 11 daysNov. 19, 21

Dec. 4Dec. 21 days

Feet.14141427

1476

785{11 days.1774177517l9{Mean of

Rhartum . .Sobat .. ..

Bahr el Gazal

Gondokoro . ., . . .Rigaf ..


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422 Lieut. NVATSON'S\Jotes on a Traverseurveyf tAteConsideringlzat the data forthe sea-level must be subject to some III1-certainty, it has not been deemed advisable to apply any correction or the

diurnalranaeof the barometer. Hypsometricalobservationshave also beellmade with evident care. But, as the hypsometercan only be regardedas asubstitute for the mercurialbarometer-the calculation of heights from itsindicationsdependingupon the barometricormula it should,when readwiththe barometer, e considered check, and preference hould be given to thebarometer. Mercurial arometers re not liable to errors,whichare of muchimportance n measurinC levations: on the contrary,hypsometerschangetheir corrections y the rise of the zeropoint due to use and aae, and a smallunknownerrorcauses a greatdiSerence n the heights. It would, therefore,be of little use to calculate these heights from the hypsometer'sreadings.The two serieswould merely serve to show by their differenceshat either thebarometers r the hypsometerswere not correct. rlthesedifferences ave beencalculatedby a shorterprocess,and it is interesting o notice how consistentlythey tell the same tale. They are as under:Flace. Date. | lI. ^ B.

y. Br. D. o Inch.Khartum .... .. .. 1874 10 9 .. - 0 30 . 0-171Mouth of Sobat .. , 6 22 .. - O 1S *.0 101Mouth of Gazal .. 187o 2 6 .. - 0 19 *.0 109Shambeh ....... .. .. e 1874 7 - .. - 0 30 *.0*174Gondokoro .. .. ,, iO 21 .. - 0-21 *.0-121

,, .. .. .. ,, 12 4 - 0-21 J 0J121EANS .. .. .. .. .. .. - 0 ' 228 * 0 * 130

Error n heighti due to H = *228 x 527 = 120 feet.,, ,, ,, B- *130 x 92-120 ,,The columnII is the correctiondue to the llypsometerson the suppositionthat the barometerswere accurate; B that due to the barometersaking thehypsometers s correct. The mean correctionE shows that the hypsometerswould have given heights on an average 120 feet lower than those deduced;

the mean of B, that if the barometers re so incorrect hc heights ought to beeducedby about120 feet. However, t i8 scarcelypossible or thebarometersto have beenincorrect o anytElingike this estent, while thecorrection orthehypsometers s not only possible but very probable. It would be interestincrto have the instruments tested at the Kew Observatory. If this could bedone, and the restllts should happen to supy)orthe inferenceshere made, itwould afford valuabIe onErnwationf the theoreticalaccuracyof the 'lnables


17/21

AKhiteile romKhartumoRigaf. 423founded on the barometrical ormula of Laplace, and the vapour tensiouformulaof Repault.It may be noticedthat the correctionsactually applied to the readings ofthe hypsometersaverage about + 0+2; and consequently the residual cor-rectiondeducednow seems to show that their zeros have risen, so that noxvthey are really moreaccurate han they were originally, he plus and miIluscorrections einOalmostnil.The comparisonsnstituted betweenthe barometerand hypsometer obser-vations aSorda convincina proof of ths fidelity with which the observationshave been made.


18/21

METEO1BOL()GI04IJBSERYATIONSaken on the WEITENILE,betweenKEBY LIEUT.WATSON .E.Temperature in Sllade.Barometer orrectedorInstrumeIltalError.

Noon12.0.A.M.ff.O P.r.8*olace.

:Ehartum .. .., .. ..OnwLiteile ..

, . ..

| Noon. P.wr.} 12.0 SO_

.. ..

.. .. . 28 ' 58.. 28'57

.. 28*58

. . 28 *63. . 28 ' 66., 28' 58. . 28 ' 66, . 28 ' 65

., 2S'64I.. i 28 70,, 1 28'64

l

A.}r I8.0;

28*58('8*66. .28 67

28 6+28 6328 6728 6528 5328 7028 -6928 7028-70

Wet,

7'268

. *73757472747575757573

Or,y.

8B77* .80 5

83-582*57989

979787976

Dry. | Wet. i Dry. Wet.

, .

* .7589

Date.

1874.Oct. 9,, 10, 11,, 12,, 13,, 14,, 15,, 16,, 17,, 18,, lg,, 20! 1 21

* !

* *S7-590 5

939193

. *

879094

* . * *

* * * *.. 8676-5 8977 8775 8873 8576 89.. 8277 8477 i 7678 7877 8 76

* 3787.S75737173

Fi


19/21

707477777577787879787776767677

* e

* .

767674767375

,, 22,, 23,, 24,, 25,, 26,, 27,, 28,, 29,, 30,, 31

Nov. 1,, 2,, 3,, 4,, 6,, 6.. 7,, 8,, 9,, 10,, 11,, 12,, 13,, 14,, 15

28 5828 5528 5328-6428-6128 5528- 6028 6328 -6528 *6528 6028- 5528- 5928 -582S s 5328 5728 5728 -5428 5528 52

. .28 4028 4128 40

* 4

,G82

. .

788078

787878798277838078767975777880787779

716g

. .

747375

* v

747475757674767575727572737371747474

8589

85 584868788868786873858687

87868384888687

74 ..73 . .73 . .7474 . .75 . .75 . .71 ..76 ..

. .

75 ..76 ..75 . .74 . .76 ..71 . .73 ..71 . .71 . .70

.. .71 . .74 ..75 . .* 1

78977797880797480

* .

7882S2777973

. 9

7o7474

. .788080

l 9

Sobat . .., 9 ..

, . ..011WhiteNile. ,. ,

, 9. ., ,,,

, ,

, ,

,

,,

. ., ..,.,

, ,

, ,Gondokoro.

28-67 ..28-61 . .28-6, ..28o66 . .28-64 28 5828 67 28 60

.. 28 G728G67 28 6028 67 28 6528G70 28-6628 67 28 6128 62 28-6028 62 28z6028*64 28-61288B2 28*5728 61 2S*5928-60 28-5828*57 28*5328-60 128-6028 61 28 5928 58 28-5628 54 28s4928X50 j 28*4628 47 28*4228 42 ..


20/21

METEOROLOGICALB8BRVATIONSalen on the WHITEILE, etween EBYLIBUT.WATSON,.E. continued.Temperaturen Shade.Barometer collected forIxlstrumental Error. Noon.12.0

7

w.Or.8.0 P.}I,8.0:Date.

1874.Nov.16,, 17,, 19,, 20

,, 21,, 22,, 23,, 24,, 2526,, 27, 28,, 29, 30

Place.

_ _

Gonclokoro. ..

.. .. ..

, . .. ..

, . .. ..

.. .. ..

. > .. ..

.. .. ..

.. .. ..

} . .. .., .. ..011WlliteNile ..

Rigaf

Noon.12.0 I)ry. 0Wet..MW8 0 P.M.8.0.

Dry. | Wet. lAry.Wet.

* )

* *

2


21/21

70

* *f

848381838079838687QN083818484S384858181

..

..

**

Dec. 1,, 2,, 3, ,, ,

traverse survey of the white nile

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