310 
Montperdu, Tarbes, 
Col du Giant, Geneva, 
Maladette, 
Pic du Midi, Tarbes, 
Cal du Giant, Chamouny, 
Montperdu, Bareges, 
Pic d’Eyre, Tarbes, 
Pic de Montaign, 
Pic du Midi, Bareges, 
Velocity of Sound 
• 
[Oct. 
3408 
18°, 7 
17.4 
-1,3 
3346 
20 ,4 
17.1 
-3,3 
3174 
17 ,4 
16 2 
-1,2 
’2858 
15 ,9 
14,6 
—1.3 
11 ,0 
+3 6 
It ,4 
+0,2 
13 ,L 
+ L5 
'+1,6 
10 ,7 
+ 3 9 
15 ,1 
4-0,5 
10 ,5 
+ 4,1 J 
2606 
17,1 
13,3 
-3.8 
2354 
18 ,1 
12 0 
—6,1 
2347 
10 ,3 
11,9 
+ 1,6 
2244 
11 ,4 
11,4 
0,0 
'1803 
10 ,3 
9,2 
-1,1 
13 ,9 
— 4,7 
13 ,1 
— 3,3 
■ 
12 ,5 
— 4,2 
—3,3 
13 .4 
-1,6 
10 8 
—3,9 
13 ,1 
—4.0 
'1163 
6 ,9 
5,9 
—1,0 
7 ,0 
— 1,1 
* 
6 ,9 
-1,0 
-2,1 
9 ,6 
—3,7 
9 ,4 
— 3,5 
f 
611 
2 ,9 
3,1 
+0,2 
537 
3 ,2 
2,7 
0,5 
415 
1 ,8 
2,1 
+0,3 
Puy de Dome, Clermont, 
Bedatdu Bagneres, Tarbes, 
Pont du Berges, Clermont, 
La Barrague, ditto, 
How the altitudes here given were found, I have not read, but probably from 
barometric observations. , - 
The mean error or difference from observations is 1 ,1. This is a degree ot 
coincidence from observations subject to so many causes of error as these are, 
could scarcely be expected. Were we to al ow only 1° tor the superior radiation 
and influence of bodies at the surface of the earth, even this trifling difference 
would disappear ; or were the observations at the same places to be repeated lit 
n io-ht instead of in the day, the time at which it is very likely they were made, it 
is "highly probable the difference would he reversed, and be positive instead of 
negative. For my part, I have no doubt that the apparently more rapid diminu- 
tion of temperature near the surface, than higher up, is owing to the observations 
having been made in the day time; and that the contrary would happen were 
they made in the night, especially if the weather was calm and clear. Dr. 
Wells’s experiments, which in the night manifested an increase of temperature of 
sometimes 12 or 16 degrees, at the elevation of only a few feet, are a strong con- 
firmation of this. 
Ill ,— .Barometric Depression . 
Unluckily 1 have not a single case by me of an elevation determined trigonome 
trically and barometrically, so that l am incapable of comparing the other formula 
with direct experiment. However, as Laplace’s empirical formula is said to lee 
exceedingly with observations, its comparison with ours will afford a tolei. y 
good indirect test. , ... „„„„„ nTlf i 
For the ease of calculation, we may suppose the temperatures 01 U . . 
lower barometer to be the same, and at 32° Fahr. or o cent, with t iese con l 
Laplace’s formula (Playfair’s Outlines, vol. i. p. 240,) is in Eug. fatioms. 
/ 2C \ P 
* * — 10050 ( 1 ) log. — 
v 1000 7 P 
And our theorem in 
C being the negative cent. temp, of the higher station, 
fathoms and logs, is, 
x ■=. < 
— >rh > orl °o‘ * = Lo g‘ ) 
+4,4164760 
