46 3[echanics, .Physics, and Chemistry.

In conclusion, the lecturer observed that every day brought to light some new fact connected with the chemistry of gas manufacture, which deserved the careful consideration of all who, like those to whom he was addressing himself, were practically engaged in this important branch of industry. He had endeavored to lay before them, with as much fulness as time allowed, the most prominent features of the ques- tion, as far as the light of science had at present elucidated them ; but the subject, in all its details, was far too complex to allow of more than a mere general statement in a compass of a single lecture.

On Scientific JExperiments in Balloons. By JAMES GLAIS~ER, Esq., F. R. S., &c.

Proceedings of the Royal Institution of Great Britain, :No. 41.

Mr. Glaisher, at the beginning, referred to the discourse given by him two years since, when he had made eight ascents, for the purpose of scientific researches, in the higher regions of the atmosphere, and said since that time he had made seventeen additional. He described the process of filling a large balloon, and briefly described a balloon ascent, speaking of the novel sensation at first experienced, of the ex- treme coldness and dryness of the air at great elevations, of the pain- less death awaiting the a6rial traveler who should ascend to an eleva- tion too great for his power of endurance, and compared it to that of the mountaiu traveler, who, benumbed and insensible to suffering, yields to the lethargy of approaching sleep, and reposes to wake no more. Moral energy in both cases, he stated, was the only means of safety.

Ite then exhibited the several instruments used, pointing out their extreme sensitiveness and delicacy, and then spoke of the primary objects of balloon research.

Subjects of Research by Means of Balloons.--lst. To determine the rate of decrease of temperature with increase of elevation ; and to as- certain whether the results obtained by observations on mountain sides, viz : a lowering of temperature of 1 ° for every increase of elevation of 300 feet, be true or not.

2d. To determine the distribution of the water, in the invisible shape of vapor, in the air below the clouds, and above them, at different ele. rations.

3d. To compare the results, as found by different instruments, to- gether :

1. The temperature of the dew point as found b y - - Dry and wet thermometers~ (free.) Dry and wet thermometers, (aspirated, or air made to pass rapidly.) Daniell's dew-point. ]tegnault's dew-point, (blowing.) Regnault's dew-point, (air made to pass rapidly.)

2. To compare the readings of- - )[ercurial and aneroid barometers, &c.

4th. Solar radiation, by taking readings of the blackened bulb ther- mometer fully exposed to the sun, with simultaneous observations of

S c i e n t i f i c . E x p e r i m e n t s in ~Balloons. 4 7

the d r y - b u l b t h e r m o m e t e r , a n d a l so o f o b s e r v a t i o n s o f H e r s c h e l ' s A c - t inomete r .

5 th . T o d e t e r m i n e w h e t h e r t h e s o l a r s p e c t r u m , w h e n v i ewed f r o m the e a r t h , a n d f a r a b o v e it, e x h i b i t e d a n y d i f f e rence ; w h e t h e r t h e r e were a g r e a t e r or less n u m b e r of d a r k l i n e s c r o s s i n g it, p a r t i c u l a r l y when n e a r s u n - s e t t i n g .

6 th . To d e t e r m i n e w h e t h e r t h e h o r i z o n t a l i n t e n s i t y of t h e e a r t h ' s m a g n e t i s m was less or g r e a t e r w i t h e l eva t ion .

P r o p a g a t i o n o f sound . A m o u n t of ozone , &c.

I n e v e r y a s c e n t a s econd or t h i r d t h e r m o m e t e r , d i f f e r en t ly g r a d u - ated, has been u sed to c h e c k t h e a c c u r a c y o f t h e r e a d i n g s of t h e d r y t h e r m o m e t e r , a n d t h e t r u t h f u l n e s s of t h e t e m p e r a t u r e s h o w n b y it. I n some of the a s c e n t s a d e l i c a t e b l a c k e n e d b u l b t h e r m o m e t e r was p l a c e d near to t he p l ace of t h e d r y - b u l b t h e r m o m e t e r , f u l l y e x p o s e d to t he s u n in c loudless sk ies , or to t h e s ky a t al l t imes . T h e r e a d i n g s of th i s i n s t r u - men t were n e a r l y i d e n t i c a l w i th t h o s e o f t h e d r y - b u l b t h e r m o m e t e r in c louded s t a t e s o f t he sky , a n d t h u s a c t e d as an a d d i t i o n a l c h e c k .

A t al l t imes , o n e or t he o t h e r , or b o t h , R e g n a u l t ' s and D a n i e l l ' s h y g r o m e t e r s h a v e b e e n used suf f ic ien t ly o f t en , a t a l l h e i g h t s , to show whe the r t h e w e t - b u l b t h e r m o m e t e r was in p r o p e r ac t ion , a n d to c h e c k the r e s u l t s g i v e n b y t h e use of t h e d r y a n d w e t - b u l b t h e r m o m e t e r on the r e d u c t i o n o f t h e o b s e r v a t i o n s .

The a u t h o r sa id he would no t g ive a d e t a i l e d a c c o u n t of t he e x p e r i - ments in t he y e a r s 1862 a n d 1868, as t h e y we re p u b l i s h e d , bu t wou ld confine h i m s e l f ' t o some of t h e r e su l t s .

H e sa id i t was soon f o u n d t h a t t he s t a t e o f t h e s k y e x e r c i s e d a g r e a t influence, a n d t h e e x p e r i m e n t s h a d to b e r e p e a t e d w i th two g r o u p s , one with c loudy sk ies , a n d t h e o t h e r w i th c l ea r sk ies .

The r e s u l t s a r e as fol low :

The Decline of the Temperature of the Air with Elevation~ when the Sky was Cloudy. Feet; Feet. Deg. Feet.

From 0 to ],000 was 4.2 from 17 experiments, or 1 degree in 223 " 1,0(~0 " 2,000 " 8.6 " 21 " 278 " 2,000 t' 8,000 " 3'7 " 22 " 271 " 3,000 't 4~9b0 " 3.4 t' 20 " 295 ~' 4~000 " 5,000 " 3.3 " 13 " 338 " 5,000 " 6~000 " 3'2 " 7 " 313 " 6,000 " 7,000 " 2"7 " 5 " 371 " 7,000 " 8~000 " 2'4 " 4 " 417 " 8,000 " 9,000 " 2"2 " 4 " 455 " 9,000 " 10,000 " 2'2 " 4 " 455 " 10,000 " 11,000 " 2"2 " 4 " 455 " 11,0130 " 12,000 " 2 2 " 4 " 455 " 12,(~00 " 13,000 " 2"2 " 4 " 455 " 13,000 ,c 14,000 t' 2"3 " 4 " 435 " 14,000 " 15,000 ~' 2.0 " 4 " 500 " 15,000 " 16,000 " 2'1 " 4 " 477 " 16,000 " 17,000 " 1'2 " 2 " 838 '~ 17,000 " 18,000 " 1.3 " 2 " 771 " 18,000 " 19~000 " 1"4 " 2 " 715 " 19,000 " 20,000 " 0"9 " 2 " 909 " 20,000 " 21,000 " 1'1 " 2 " 911 " 21,000 ~' 22,000 " 0"8 " 2 " 1,250 ~' ~2,000 " 23~000 " 0"8 " 2 " 1,250

48 Mechanics, _Physics, and (dhemistry. These results show, when the sky is cloudy, the decline of tempera-

ture at every 1000 feet increase of elevation. Up to 5000 feet the number of experiments upon which each result is based vary from 18 to 22; at 6000 and 7000 feet to 7 and 5, respectively; from 7000 to 16,000 feet to 4 ; these having been made on two days, viz : 1868, June 26 and September 29, on which days the balloon was frequently enveloped in fog and clouds to the height of three and four miles, and those above 16,000 feet on the former of these two days only, during the ascent and descent, the sky being still covered with cloud when the balloon was between 4 and 5 miles high. The Decline of the Temperature of the Air with Elevafion, when the Sky was Clear,

or chiefly Clear. Feet . F e e t . D e g . Fee t .

F r o m 0 t o 1 , 0 0 0 w a s 6 . 2 f r o m 9 e x p e r i m e n t s , o r 1 d e g r e e in 1 6 2 , , 1 , 0 0 0 " 2 , 0 0 0 " 4 . 7 , , 9 2 1 3 ,, 2 , 0 0 0 " 37(~00 ' , 3 . 8 " l l " 2 6 4 - 8 , 0 0 0 " 4 , ¢ 0 0 " 3 3 , , 1 2 , , 3 0 4 , , 4 , 0 0 0 " 5 , 0 0 0 , ' 2 . 9 " 1 2 ,, . 3 4 5 , , 5 , 0 ( t 0 " 6 ,0 t~0 " 2 . 6 , ' 1 7 , , 3 8 5 - G 0 0 0 " 7 , 0 0 0 " 2 . 5 " 1 5 , , 4 0 1 - 7 , 0 0 0 " 8 , 0 0 0 " 2 . 7 " ] 2 , ' 3 7 1 , , 8 , 0 0 0 " 9 , 0 0 0 " 2 . 5 " 1 2 , , 4~bo " 9 ~ 0 0 0 " 1 0 , 0 0 0 " 2 ' 4 " 1 2 " 4 1 7 " 1 0 , ~ 0 0 " 1 1 , 0 0 0 " 2 " 6 " 1 8 " 3 8 5 " l l , ( ~ 0 0 " 1 2 7 0 0 0 " 2 . 3 " 1 1 " 4 3 5 " 1 2 , 0 0 0 " 1 3 , ( 0 0 " 2 ' 2 " 1 1 " 4 5 5 " 1 3 ~ 0 0 0 " 1 4 , ~ , 0 0 " 2 " 0 " 1 1 " 5 ( , 0 " 1 4 , 0 0 0 " 1 5 : 0 0 0 " 1"7 " 9 - " 5 8 8 " 1 5 , 0 ~ 0 ,t 1 6 , 0 0 0 " 2"2 " 9 " 4 5 5 " 1 6 , ( 0 0 t ' 17jO(:O t ' 1 ' 9 " 7 " 5 2 6 " 1 7 , 0 0 0 " 1 8 , 0 0 0 " 1 - 7 " 7 " 5 8 8 " 1 8 , 0 0 0 " lO,q ,O0 " 1"5 " 7 " 6 6 6 " 1 9 , 0 0 0 " 2 0 , 0 0 0 " 1 ' 3 " 7 " 7 7 1 , , 2 0 , 0 0 0 " 2 1 , 0 0 0 " 1 . 2 " 7 " 8 3 3 , ' 2 1 , ( ! 0 0 " 2 2 , 0 ( , 0 " 1 . l " 7 " 9 1 1 " 2 2 , 0 ( 1 0 " 2 3 , 0 0 0 " 1 ' 0 " 4 "' 1 , ( 0 i ) ~' 2 3 , L 0 0 " 2 4 , 0 0 0 " 1 . 3 " 2 " 7 7 1 , , 2 4 , 0 ( 1 0 " 2 5 , 0 f : 0 " 1 ' 1 " 2 " 9 ~ 9 ' , 2 5 ~ 0 ( i 0 " 2 6 , 0 ( J 0 " l ' 0 " 1 " 1 , 0 0 0 " 2 6 , 0 0 0 " 2 7 , 0 0 0 " 1 . 0 " 1 " 1 ,OD0 " 2 7 , 0 C 0 " 2 8 , ( 1 0 0 " 0 ' 9 " 1 " 1 , H 1

1 " 1 , 2 5 0

the number of experiments vary " 28 ,000 " 297000 " 0"8 "

Up to the height of 22,000 feet from 7 to 17, and there can be but little doubt that the number sho~'- ing the decrease of temperature are very nearly true, and approximate closely to the general law. Above 24,000 feet the number of experi- ments are too few to speak confidently upon them, but they are in accord- ance with the series deduced from the experiments at less elevations.

A decline of temperature under a clear sky of 1 ° takes place within 100 feet of the earth, and at heights exceeding 25,000 feet it is neces- sary to pass through 1,000 feet of vertical height, as appears in the last column of the preceding table, for a decline of 1 ° of temperature.

By adding together, successively, the decline of temperature for each 1000 feet the whole decrease of temperature from the earth to the different elevations is found. The results, with a cloudy sky, are as follow :

~¢ientifie Experiments in Balloons. Whezt the S k y w a s Cloud?f.

Feet. Feet. Deg. Feet. From 0 to 1 , 0 0 0 the decrease was 4 . 5 o r 1 d e g . o n the average of 2 2 3

0 " 2 , 0 0 0 " 8"1 " 2 4 7 ~t

" 0 " 3 , 0 0 0 " 11"8 " 2 5 5 " 0 " 4 , 0 0 0 " 15"2 " 2 6 3 " 0 " 5 , 0 0 0 " 18"5 " 271 " 0 " 6 , 0 0 0 " 2 1 . 7 " 2 7 7 " 0 " 7 , 0 0 0 " 24"4 " 2 8 7 " 0 " 8 , 0 0 0 " 26"8 " 2 9 9 " 0 " 9~000 " 2 9 ' 0 " 311 " 0 " 1 0 , 0 0 0 " 3 1 ' 0 " 321 " 0 " l l ,OOO '~ 33"0 " 3 2 9 " 0 " 1 2 , 0 0 0 " 3 5 - 6 " 3 3 7 " 0 " 1 3 , 0 0 0 " 3 7 ' 8 " 3 4 4 " 0 " 1 4 , 0 0 0 " 40"1 " 3 4 0 " 0 " 1 5 , 0 0 0 '~ 42"1 " 3 5 6 " 0 " 1 6 , 0 0 0 " 44"2 " 3 6 2 " 0 . ' 1 7 , 0 0 0 " ~ . 4 " 3 7 5 " 0 " 1 8 , 0 0 0 " "7 " 3 8 6 " 0 " 1 9 , 0 0 0 " 4 8 . 1 " 3 9 5 " 0 " 20,001) " 4 9 " 0 " 4 0 9 " 0 " 2 1 , 0 0 3 " 50"1 " 41;~ " 0 " 2 2 , 0 0 0 " 50.9 " 4 3 2 " 0 " 2 3 , 0 0 0 " 5 1 ' 7 " 4 4 5

49

These results, showing the whole decrease of temperature of the air from the earth up to 23,000 feet, differ very considerably from those with a clear sky, to be spoken of presently. The number in the last column show the average increment of height for a decline of 1 °, as found by using the temperature of the extremities of the column alone. To 1000 feet high the average is 1 ° in 223 feet, increasing gradually to 1 ° in 445 feet at 23,000 feet.

W h e n t h e S k y w a s C l e a r , o r ch ie f l y C l e a r .

Feet. Feet. D e g . F e e t .

F r o m 0 to 1 , 0 0 0 the decrease was 6.2 or I d e g . o n t h e average of 1 6 2 " 0 ,t 2 , 0 0 0 . " 10"9 " 1 8 4 " 0 " 3 , 0 0 0 " 14"7 " 2 0 4 " 0 ~' 4,1)03 " 18"0 " 2 2 3 " 0 " 5 , 0 0 0 " 2 0 4 ) " 2 3 0 " 0 " 6 , 0 0 0 " 2 3 . 5 " 25(; " 0 t, 7 , 0 0 0 t ' 2 6 " 0 " 271 " 0 " 8 , 0 0 0 ,, 2 8 . 7 " 2 7 9 " 0 " 9 , 0 0 0 " 3 1 ' 2 " 2 8 0 " 0 " 1 0 , 0 0 0 " 33-6 " 2 9 S " 0 ,t 1 1 , 0 0 0 " 3 5 ' 6 " 30!~ " 0 " ] 2 , 0 0 0 " 37"9 " 3 1 7 " 0 " 1 3 , 0 0 0 ~' 40"1 " 3 2 4 " 0 " 1 4 , 0 0 0 " 42"1 " 33"3 " 0 " 1 5 , 0 0 0 " 4 3 " 8 " 3 4 3 " 0 " 1 6 , 0 0 0 ~' 4 6 ' 0 " 3 4 8 " 0 " 1 7 , 0 0 0 " 4 7 ' 9 " 3 5 5 ' t 0 " 1 8 , 0 0 0 " 4 9 ' 6 " 3 6 3 " 0 " 1 9 , 0 0 0 " 5 1 ' 1 '~ 3 7 2 " 0 " 2 0 , 0 0 0 't 5 2 " 4 " 3 8 2 " 0 " 2 1 , 0 0 0 " 53"6 ' t 3 9 2 " 0 " 2 2 , 0 0 0 " 5 4 ' 7 " 4 0 5 " 0 " 2 3 , 0 0 0 " 5 5 ' 7 " 4 1 3

VOL. L I I . - - T H I R D S E R I E S . - - N O . 1 . - - J U L Y , 1 8 6 6 . 5

$0 Mechanics, Ph~/~'e,, and C~eraistry, F e e t , : ~ e e t . D e g . i ~ e e L

From 0 to 24,OOO th~ decrease was 57.0 or 1 deg. on the average of 422 " 0 " 2 5 , 0 0 0 " 5 8 " 1 " 4 3 1

" 0 t, 2 6 , 0 0 0 ' t 5 9 ' 1 " 4 4 1 " 0 " 2 7 ~ 0 0 0 " 6 0 1 " 4 4 9

" 0 " 2 8 , 0 0 0 ~' 6 1 ' 0 " 4 5 9

" 0 " 2 9 , 0 0 0 " 6 1 ' 8 " 4 6 9

" 0 " 3 0 , 0 0 0 ~ ' 6 2 ' 3 " 4 8 2

These results, show'rig the whole decrease of temperature from the ground to 80,000 feet, differ greatly, as just mentioned, from those with a cloudy sky.

The numbers in the last column, showing the average increase of height for a decline of 1 ° of temperature from the ground to that elevation, are all smaller than those with a cloudy sky at the same elevation. Each result is based upon at least seven experiments, taken at different times of the year, and up to this height considerable con- fidence may be placed in the results, They show that a change takes place in the first 1000 feet of 1 ° on an a#erage in 162 feet, increasing to about 800 at 10,000 feet. In the year 186'2 this space of 300 feet was at 14,000 feet high, and in 1863 at 12,000 feet. Therefore the change of temperature has been less in 1863 than that in 186 ° , and less in 1864 than in 1863, but the experiments have all been taken at different times of the year.

Without exception the fall of 1 ° has always taken place in the smallest space when near the earth.

Treating the observations for determining the degrees of humidity of the air in the same way, the following are the results :

When the sky was cloudy, saturation being considered as 100, the degree of humidity on the earth was ................................ 74 from 19 experiments.

At 1,000 feet ....................................... 76 ', 33 ~, - 2 , 0 0 0 " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6 " 3 4 "

' , 3 , 0 0 0 " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8 " 3 5 "

, , 4 , 0 0 0 " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5 " 2 7 "

- 5 , 0 0 0 " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4 " 1 6 "

' , 6,t)OO " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8 " 1 4

" 7 , 0 0 0 " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2 " 11 "

" 8 , 0 0 0 " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 " 1 1 "

" 9 , 0 0 0 " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 0 " 1 1 "

" IO,OCO " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 8 " 1 0 "

" 1 1 , 0 0 0 ' , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 7 " 1 0 "

" 1 2 , 0 0 0 " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 " 6 "

" 13 ,1~00 " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 8 " 6 "

" 1 4 , 0 0 0 " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 " 5 "

,c 1 5 , 0 0 0 ' , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 9 " 3 "

'~ 1 6 , 0 0 0 '~ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 9 " 2 "

" 1 7 , 0 0 0 " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 7 " 2 "

" 1 8 . 0 0 0 " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3 " 2 "

" 1 9 , 0 0 0 " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 4 " 2 "

" 2 0 , 0 0 0 " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 9 '~ 2 "

" 2 1 ~ 0 0 0 " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2 " 2 "

" 2 2 , 0 0 0 " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4 " 1 "

" 2 3 , 0 0 0 " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 0 " 1 "

The law of moisture here shown is a slight increase from the earth to the height of 3000 feet, and then a ~light decrease to 6000 feet, the degree of humidity being at this elevation nearly of the same value as on the ground. From 6000 to 7000 feet there is a large decrease,

Scientific ~Experimtat, in Balloons. 51

and then an almost uniform decrease to 11,000 feet ; it increases from 12,000 to 16,000 feet, and then decreases ; the number of experiments up to l l ,000 feet vary from 10 to 33; and I think good confidence may be placed in the result to this elevation, but at heights of !2,000 fee~ the number of experiments ~re evidently too small to speak with any confidence in respect to the results.

By tresting the results with a clear, or a nearly clear sky, ia the s~me way, the following results were obtained:

W i t h a d e a r s k y t h e d e g r e e o f h u m i d i t y o n

t h e g r o u n d w a s , , . , , . . . . , . . . . . , . . , . . . . . . . . . . . , 5 9 f r o m 0 A t 1 , 0 0 0 f e e t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1 " 1 4

- 2 , 0 0 0 - , . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . ~ . . . . . . 7 0 " 1 7

" 3 , 0 0 0 ~' 4 , 0 0 0

' 5 , 000 " 6 , 0 0 0

" 7 , 0 0 0 " 8 , 0 0 0

" 9 , 0 0 0 " 1 0 , 0 0 0 " 1 1 , 0 0 0 " 1 2 , 0 0 0

" 1 3 , 0 0 0 " 1 4 , 0 0 0 " 1 5 , 0 0 0 " 1 6 , 0 0 0 " 1 7 , 0 0 0 " 1 8 , 0 0 0 ~' 1 9 , 0 0 0 ~' 2 0 , 0 0 0

~' 2 1 , 0 0 0

• ~ 2 2 , 0 0 0

e x p e r i m e n t ~ .

" 7 1 " 2 3 "

- t i9 " 1 7 ~'

" 15 '~ , , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (;2 ~' ~ 6

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 6 " 1 6 * ' " . . . . . , . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . 5 0 '~ 1 4 " " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5{) '~ 9 "

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 6 " 1 8 " 4 3 ~ ' 1 0 "

. . . . . . y . . . . . . . . . . . r e ~ . . . . . . . . . . . . . . . . . .

, , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 5 " 8 "

" . . , , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 7 " 7 "

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 7 ~ ' 7 "

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . 4 4 " ~ ' ~' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 0 ~ ' 5 " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 9 ~' 4 " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 " 2 " " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 6 " 2 " 6 6 ~ .

*~ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . q 2 " 1 / ' " 2 1 z l "

~' 2 3 , 0 0 0 ~ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 6 ~ 1

The law of moisture here shown is a slight increase to 1000 feet, a considerable increase between 1000 and 2000 feet, a nearly constant degree of humidity from 2000 to 5000 feet, and a gradual decrease after- wards to 12,000 feet. At greater heights the numbers are less regular. The results up to 11,000 feet are based upon experiments varying from 10 to 20, and are most likely very nearly true normal values. At heights exceeding 12,000 feet the number of experiments have varied from 1 to 8, and no general confidence can be placed in them.

By comparing the results fi'om the two states of the sky, the degree of humidiSy of the air up to 1000 feet high is 15 less with a clear sky than with a cloudy; from 2000 to 5000 is from 4 to 6 less; at 6000 feet the air with a clear sky is much drier than at 5000 feet, but wi th a cloudy sky it is nearly of the same degree of humidity, so that the difference between the two states is large, amounting to no less than 11; the difference decreases to 0 at 9000 feet, but increases to 4 a: 11,000 feet ; at heights exceeding 11,000 feet the air with clear skies generally becomes very dry, but with cloudy skies frequently becomes more humid, as was to be expected from the fact of the presence of clouds at heights exceeding three and four miles.

In both states of the sky, a t extreme elevations, the air becomes very drvv, bz~t~ s o f a / a s my experiments go, is never free fro, , water.

( T o b e c o n t i n u e d . )