298 



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. 



Table I 



fa 



be 



< 



Rainfall 

 Per cenit. 



0.82 

 2.3 



0.45. 0.23 0.16 

 1.3 !0.6 0.4 



.07 4.14 

 0.2 11.6 



11.25 

 31.5 



10.54 

 29.5 



5.10|2.52 

 14.3 7.1 



0.31 

 0.9 



0.14 

 0,4 



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 



