IN THE MONTH OF FEBRUARY, 1842. 173 
—_> 
sy) \ 
e"" 502 hy 
Mahabuleshiwar, — 
80 
Bombay _— 
23 XY 
oonaly 
{es 32 
4 NE senome ne Madras 
ee 
J823 
and it falls wholly from June to October, under the south-west monsoon. This wind 
blows over a range of mountains varying from one thousand to eight thousand feet in 
height. At Mahabuleshwar, at an elevation of four thousand five hundred feet, the fall 
of rain, in 1834, was three hundred and two inches, and almost wholly with the south- 
west monsoon. At Poonah, on the eastern side of the mountains, elevated one thousand 
eight hundred and twenty-three feet, the annual fall of rain is only twenty-three inches, 
while, at Madras, it is thirty-two inches. By the interposed range of mountains, the 
humid air from the ocean is cooled, and the windward slope of the mountain is deluged 
with rain. The case is quite analogous with a southerly wind in the United States. A 
south wind from the level of the sea encounters land every where swelling to the height 
of several hundred feet, and rising in ridges and insulated peaks to the height of four or 
_ five thousand feet. A copious precipitation must be the consequence. But it is not 
wholly by elevation that the rain is caused; the effect is increased by collision with the 
upper current flowing in a different direction. The winds marked on the charts are 
merely surface winds; but from the observations, pages 166 and 169, there is reason to 
believe that the whole upper part of the atmosphere was pursuing its course undisturbed 
from the south-west or west over the entire United States. Suppose the lower current 
coincide in direction with the upper: then the whole atmosphere moves on as one mass, 
there is no mingling of strata of unequal temperature, and no cause for the formation of 
cloud. Suppose, however, the direction of the lower stratum is changed, while that of 
the upper continues, then we have two currents rubbing upon each other, generally of 
unequal temperature, differing also, perhaps, in their amount of moisture. There will 
be a partial mingling, and, of course, cloud formed. It seems then hardly possible that 
the lower current should change its direction to a warmer quarter, and continue thus 
for many hours without the formation of cloud, and followed by the production of rain. 
The effect of an elevated ridge of land appears sensible in the difference of climate 
upon the two sides of the Alleghanies. The region immediately west of that range of 
mountains has a sensibly greater degree of cloudiness, (particularly in winter,) than 
places on the east side. ‘This appears from the following table of averages, (0) represent- 
ing a sky perfectly clear, (10) entirely overcast. 
HUDSON, 0. HANOVER, N.H. CAMBRIDGE, MASS. 
9a. M.| 3 P.M. Banrise 13 p.m.| 92 P.M.||Sunrise] 9 a. M.| 8 p. “i 9 P.M. 
Spring, 5.70 | 5.91 3.93 | 4.02 | 3.55 5.50 | 5.80 | 6.33 | 5.53 
Summer,) 5.22 | 5.57 | 5.48 | 3.41 | 2.92 || 5.43 | 5.28 | 5.88 | 4.90 
Autumn,) 5.96 | 6.20 || 5.66 | 4.34 | 3.54 || 5.77 | 5.60 | 5.93 | 4.53 
Winter, 8.07 | 7.87 4.65 | 4.80 | 4.14 5.20 | 6.00 | 5.67 | 4.80 
| re 
Year, | 6.24] 6.39 | 4.92! 4.02] 3.54 !! 5.47! 5.661 5.81! 4.94 
VOL. IX.—-4'7 
