464 — REPORT—1862. 
variation, but during which time there was a great increase of temperature, 
and consequently the relative humidity decreased with rapidity from 95 to 39. 
The balloon then fell from 19,500 feet to 19,200 feet, the temperature of the 
air decreased to 38°, and the dew-point increased from 193° to 21°, and the 
humidity increased to 49. After 19,200 feet the dew-point decreased with 
rapidity to 16° at 20,000 feet, with a humidity of 48; and afterwards with 
great rapidity to a dew-point of less than —12° at 21,000 feet; and at 
heights exceeding this the dew-point is unknown, but was certainly lower 
than —20°, and probably as low as —30° up to 24,000 feet ; from the ob- 
servations of the dry- and wet-bulb thermometers it seems to have been as 
low as —50° at 25,000 feet ; therefore the tension of vapour above 20,000 feet 
must have varied from about 0-015 in. to less than 0-01 in., and the degree 
of humidity to have decreased to 2, or even less. In this series we can 
distinctly trace a stratum of moist air in the cloud above 4000 feet, and 
again between the heights of 9500 feet and 11,500 feet. From 11,500 feet 
to 19,000 feet the tension of vapour differed but very little from 0°13 inch ; 
then the amount of water present in the same mass of air was nearly constant 
for 8000 feet in vertical height; immediately after this there were some 
irregularities, and above 20,000 feet the air was dry, being almost free from 
vapour. 
Tare VII. (continued.) 
Humidity of the Air. 
Ascending. Descending. 
Height, in feet, 
wpe ire sam Tempe Degree Tempe Degree 
level of the sea. |Between Circum-jrature of Elastic of [Between Cireum-|rature of Elastic of 
what stances. |the dew- force of | numi- || bat | stances.|the dew-| ree Of humi- 
times. point. vapour. dity. times. point. vapour, dity. 
July 30. g 3 in. 7 FA in. 
6000 4.8 33°8| ‘194] 68 || So ose 33°0| 188] 61 
5000 go = B72 | 222). 166. |] ae 36°7.| ‘218}. 67 
4000 2a 1. a 39°5) 242) 63 || w eer eee 38°5| °233] 66 
3000 ee 41-4| °261| 65 a eke 42°3| °270} 65 
2000 gu 43°2| °279| 54 || = BP see 41°8| °265| 53 
1000 ee 44'2| *290] 51 B B | oo 45°8| °308] 52 
° Fe 530] *403| 54 || § oe 474} °328) 48 
July 30.—The temperature of the dew-point in this ascent was constantly 
varying: on the ground it was 53°, at 1000 feet it was 441°, but at interme- 
diate points it was sometimes on one side and sometimes on the other, to the 
amount of 1° or 2° from the curve-line joining these points ; then up to 2400 
feet there was a stratum of moist air, and above 3600 feet there were strata of 
moist and dry air alternately for 2000 feet ; higher than this there was a 
stratum of dry air from 5600 to 6400 feet, and higher still one of moist from 
6500 feet to the highest point reached: these terms, moist and dry, have 
reference to a curve-line, which was made to pass near every point as laid 
down from observation ; and the same phenomena generally prevailed during 
the ure The relative humidity generally increased to the highest point 
reached, 
