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THE JOURNAL OF INDIAN BOTANY,
Rainfall. The mean annual rainfall for Allahabad, calculated in 1913 (7), is 37*51 inches; other calculations put it as high as 10 inches. The distribution of this fall is indicated in Table I and Fig.
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Mean monthly rainfall in inches, and percentage for each month, for Allahabad.
From this table it will be seen that 91 per cent, of the rainfall occurs during the months of June to October, while only about 1 per cent, falls during March, April, and May. The rainfall is remarkably uniform from year to year (8). In 11 years a deviation of 33 per cent, or more above normal has been observed but seven times, and a corresponding diviat'on be'ow normal but six times. The greatest recorded rainfall was 76"25 inches in 1891, and the lowest 16'82 inches in 1861.
During the monsoon the rains are at times torrential, at other times gentle and lasting for one or more days- The soil is baked hard by the intense heat and drought of spring, and wherever drainage has been established the more violent rains quickly run off. Under such conditions erosion is heavy, and the soil is wet only to a slight depth. After unusually heavy rains the level areas become vast shallow seas ; one may travel for miles along the railways and see no land except the railway embankment and the mounds on which villages are situated. Water is retained in the shallow depres- sions, from which it disappears at length by evaporation and by use for irrigation. In consequence, where there is good drainage there is little accumulation of water in the soil, but where drainage is poor, the soil, or at least the surface soil exploited by plants, is saturated.
Insolation. Little has been done with this climatic factor. The Meteorological Observatory has kept hourly observations of cloudi- ness, using the usual scale of — 10, where indicates a cloudless sky, and 10 indicates the sky completely overcast by dense clouds or low fogs. Such a record is necessarily a matter of judgment, and is of no great value in the study of climatic factors. We have nothing to indicate what proportion of the solar energy is in the form of
