330 M. Humboldt’s Observations on the Horary 
extreme annual variations are at the same hours, near the equa- 
tor, from 4 to 4^ millim. ; near the tropic of Capricorn, 21 
millim. ; near the tropic of Cancer, from 25 to 30 millim. 
9- Under the tropics, as in the temperate zone, on comparing 
the extreme variations of the barometer month by month, the 
limits of the ascending oscillations are found two or three times 
nearer than the limits of the descending oscillations. 
10. The observations which have been hitherto collected have 
not indicated a sensible influence of the moon upon the oscilla- 
tions of the atmosphere ; these oscillations appear owing to the 
sun, which acts, not by the attraction of its mass, but as a calo- 
rifying planet. If the solar rays produce periodical changes in 
the atmosphere, there remains to be explained, why the two 
barometrical minima nearly coincide with the warmest and cold- 
est periods of the day and night. 
Table of Observations of Horary Variation made between the 
parallels of Lat. 25° ♦S'., and Lat. 55° N. from the level of the 
Ocean to 1400 toises of elevation. 
TORRID ZONE, 
•g 
3> 
<D 
£ 
<D 
® £ 
PLACES OF OBSERVATION. 
inima of 
Night. 
a £ 
.§| 
aa> 
O . 
Sq 
a 
-xima of 1 
Evening. 
III 
Hiss 
fasl 
OBSERVERS. 
S 
s! 
s 
C3 
s 
|O.SS 
Equatorial Atlantic Ocean, 
Equatorial America, be- 1 
4 h 
I 0 h 
4 h 
10 h 
... 
Lamanon & Monges. 
tween Eat. 23° N. and j 
12 ° S. to 1500 toises of) 
4£ 
94 
41 
11 
2.55 
Humbolt & Bonpland. 
height, - - j - 
Payta (Peru), Lat. 5° 6 ' S. 
3 
9 
31 
114 
3.40 
Duperrev. 
Guayra, Lat. 1 0 ° 36' N. 
Bogota, Lat. 4° 35' N. ) 
... 
94 
9 
34 
10 
2.44 
Boussingault & Rivero. 
Height 1366 toises. j 
4 
4 
10 
2.29 
Indian and African Seas, \ 
84 
Horsburgh. 
Lat. 10 ° N. 25° S. j 
4 
4 
11 
... 
Equatorial Pacific Ocean, 
34 
94 
4 
101 
LangsdorfF & Horner. 
Sierra Leone, Lat. 8 ° 30' N. 
5 
94 
3| 
10 
Sabine. 
Mysore, Lat. 14° 11' N. } 
height 400 toises. — V 
5 
104 
4 
101 
Kater. 
(Rainy Season), - j 
Pacific Ocean, between l 
Lat. 24° 30' N. and 25° S. y 
34 
94 
34 
9| 
... 
Simon off. 
Macao, Lat. 22° 12' N. 
Calcutta, Lat. 22° 34' N. 
5 
9 . 
5 
10 
Richelet. 
6 
94 
6 
10 
... 
Balfour. 
Equinoctial Brazil, at Rio ) 
Janeiro, (Lat. 22° 54 / j 
O 
0 1 
A 
11 
2.31 
f Dorta, Freycinet, 
4 Eschwege. 
S.) and at the missions j 
of the Coroatos Indians, j 
o 
4 
