RELATION TO THE DISTRIBUTION OF BAROMETRIC PRESSURE. 
3G5 
pressure at 10,000 feet is very fairly exact, as may be seen by comparing the wind 
directions on Plate 19 with the isobars on Plate 20. For greater elevations I have 
only the evidence of the Allahabad nephescope, by means of which the directions of 
movement of the cirrus clouds has been observed for eight years. These observations 
were recorded and originally tabulated to 16 points, but in giving them here I have 
reduced the number of points to 8. The total number of observations, during the 
eight years 1878-1885, inclusive, with the resultants computed by Lambert’s 
formula, are given in Table XV. 
Table XV.—Observed Movements of Cirrus Clouds at Allahabad during the years 
1878-85. 
Month. 
N. 
N.E. 
E. 
S.E. 
S. 
s.w. 
W. 
N.ff. 
Resultant. 
Direction. 
Percentage. 
January .... 
1 
27 
44 
20 
S. 87° W. 
84 
February .... 
2 
i 
3 
18 
55 
9 
S. 85° W. 
83 
Marcli. 
1 
2 
3 
3 
28 
58 
8 
S. 77° W. 
79 
April. 
2 
i 
1 
10 
31 
15 
N. 86° W. 
80 
May. 
. . 
8 
22 
7 
S. 89° W. 
88 
June. 
6 
6 
4 
2 
15 
24 
7 
S. 77° W. 
43 
July. 
4 
10 
3 
4 
6 
8 
3 
S. 6 P E. 
14 
August .... 
2 
6 
10 
2 
1 
7 
9 
4 
N. 33° W. 
5 
September 
2 
4 
11 
5 
3 
6 
9 
3 
S. 28° E. 
8 
October .... 
1 
1 
1 
7 
5 
1 
S. 63° W. 
58 
November. . 
i 
, , 
i 
4 
6 
2 
S. 82° W. 
73 
December .... 
1 
21 
17 
3 
S. 68° W. 
88 
The resultants for January, May, and October are consistent with the distribution 
of pressure at 10,000 feet, but that for July has too large a southerly component. 
The very small percentages of steadiness for the three rainy months of July, August, 
and September, however, indicate that the pressure gradients of the rainy monsoon 
are evanescent at the level of the cirrus clouds. 
As regards the country north of the parallel of 24° and west of the meridian of 
86° E. longitude, the distribution of pressure in October is strikingly similar to that 
which obtains in May, but the gradients are much less steep. Therefore, although on 
account of the large diurnal range of temperature, convective interchange may be 
quite as active in October as in May, the winds which blow in the afternoons are not 
nearly so strong. In Table XVI., the maximum gradient through Lucknow, at 10,000 
feet above sea-level, is compared with the gradient at sea-level and with the mean 
wind velocity at North-Western Provinces stations, for each of the four months under 
review. 
