294 INDIAN METEOROLOGY. 



The observed facts are thus described by Mr. Blanford : — 



"A fall of snow on the hills ii followed, as soon as the weather clears, by a consider- 

 able rise of pressure over the mountains, and frequently also over the north-western 

 plains, and this rise is accompanied by a steady wind on the plains, from north along 

 the foot of the hills; from north-west on the more distant plains. In the cold weather 

 and early spring, when there is often rain simultaneously on the plains, there is also a 

 considerable fall of temperature ; but in April frequently, and generally in May, there 

 is no rain on the plains, and any fall of temperature is restricted to the immediate 

 neighbourhood of the hills. In these months the cooling effect of ihe snow is local, 

 but it is also persistent ; and since the snow reflects a large portion of the sun's rays, 

 and that which is absorbed does not raise the temperature of the surface, nor that of 

 the air resting on it, above the freezing point, this air remains denser than it would be 

 over a bare rock surface. It floats away as a north-west wind at a high level, towards 

 the plains communicating its high pressure and southward movement to the lower 

 strata, and thus the whole mass of dry air moves towards the region of low pressure 

 (which then exists over the plains of Behar, Bengal, and the peninsula), constituting 

 the dry land winds, usually characteristic of the spring, and in seasons of unusual 

 snowfall lasting into the summer months. These winds are hot, the heat being 

 absorbed from the dry strongly-heated land surface, and the lower strata, thus heated, 

 mingle by convection with the higher, while the latter descending are also heated, 

 partly by the compression, which the air necessarily undergoes, partly by being 

 brought within the healing influence of the ground." 



During the same year a chart of the average rainfall of India was 

 drawn on a map of 64 miles to the inch and displayed at the 

 Amsterdam Exhibition, and also prepared for reproduction by 

 lithography. The chart accompanying it shows the names of 985 

 places, with the average rainfall of each to the nearest integral inch, 

 while the distribution of rainfall is shown by eight tints, representing 

 respectively the areas with an annual fall below 5 inches and successive 

 increments up to above 100 inches. The only general rainfall charts 

 of India previously published were, first, that drawn in 1872 by Dr. 

 (now Sir) D. Brandis, the late Inspector-General of Forests, when 

 engaged in the preparation of his work on the Indian Forest Flora, 

 and published in Vol. II., No. 7, of Ocean Highways, and, second, 

 a revised edition of the same chart, prepared in Mr. Blanford's 

 office and published in 1878. 



Progress was made by Mr. Blanford with the discussion of the 

 rainfall data of past years and by Mr. Eliot in the study of the 

 origin and development of storms, by his paper (printed in Part I., 

 Volume II., of the Indian Meteorological Memoirs) on a small 

 cyclonic storm which originated over the Bay of Bengal, and thence 

 travelled northwards across Bengal in the third week of November 

 1878. He showed that the origin, existence, and motion of the 

 storm were due entirely to the atmospheric conditions of the area 



