ON EIGHT BALLOON ASCENTS IN 1862. 453 
ft. feet. z feet. 
From 0 to 10,000 the decrease was 36:7, or 1° on the average of 272 
id 11,000 u 39°3 es 279 
i; 12,000 % 41:9 i. 286 
<3 13,000 ifs 44-4 a 293 
i 14,000 ¢ 46-6 ia 300 
. 15,000 a 48-7 Bs 308 
3 16,000 “ 50°8 m8 314 
Re 17,000 a 52-7 z 322 
As 18,000 ao 54:5 nf 330 
Fy: 19,000 - 56:3 Ee 337 
4 20,000 i 57°8 = 346 
% 21,000 4 59-1 ee 355 
2 22,000 on 61:4 i 358 
a 23,000 is 62-4 sf 368 
as 24,000 ae 63:7 5s 377 
M 25,000 <3 64:8 s 386 
* 26,000 + 65:°8 i 396 
- 27,000 * 66:8 = 404 
= 28,000 fe 67-7 3 413 
_ 29,000 + 68°5 23 423 
3 30,000 70-0 he 428 
These results, showing the whole decrease of temperature with different 
elevations, differ considerably from those which would be found on the sup- 
position of a decline of 1° of temperature for every 300 feet. The observed 
decrease in the first 1000 feet, viz. 7°-2, is more than double of that given on 
this supposition, viz. 3°°3, and the observed values are all greater at the 
lower elevation ; but the difference between the two becomes less and less, till 
at the height of 14,000 feet they agree. At greater elevations they again 
differ, but in the contrary way, the observed values being now the smaller,— 
the differences between the two increasing with increased elevation, till at 
30,000 feet the difference amounts to no less than 30°—the observed values 
showing a decline of 70°, and theory a decline of 100°. 
The numbers in the last column show the average increment of height for 
a decline of 1°, as found by using the temperatures of the extremities of the 
column alone; and they do not differ much from those found by Gay-Lussae, 
Rush and Green, and Welsh, at the same elevations. 
At 14,000 feet the average is the same as that of theory, viz. 1° in 300 
feet; and certain it is, in any balloon ascent exceeding 8000 feet, where the 
average decrement is 1° in 254 feet of ascent, and up to 20,000 feet, where 
the average is 355 feet, that such results would have been looked upon as 
generally confirming the above theory, and hence the necessity of including 
observations before leaving and near to the earth, and extending them to the 
highest point possible. 
Respecting the rate of the decrease of temperature with height, it is 
abundantly evident that much uncertainty would always prevail, how great 
soever the accumulation of observations of mountain temperature might be, and 
the only means of determining this important element is by balloon ascents. 
In the preceding Table it will be seen that the decrease of temperature in 
the first 5000 feet exceeds 23°, and that even in cloudy states of the sky it 
amounts to 20°. So large a decrease of temperature taking place, whether 
the sky be clear or cloudy, within the first 5000 feet of the earth, it became 
very desirable, and indeed necessary, to ascertain how this change of tempe- 
