92 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



the surface of the earth, while the quantity of moisture at 

 that altitude is, during August, from a fourth to a fifth, in 

 September an eighth, and in April less than a tenth of that 

 observed at the surface of the earth; fifth, at altitudes of six 

 or seven thousand meters the absolute humidity is very small 

 throughout the year, and less than one grain of vapor is to be 

 credited to every cubic meter of air; but at the greatest 

 altitudes that have been reached there has been found no 

 perfectly dry air. Thus the relative humidity increases as 

 we ascend from the earth's surface until we reach the level 

 of complete saturation, but above the clouds the diminution 

 of relative humidity diminishes suddenly. The ordinary 

 condition of the atmosphere appears to be that of successive 

 layers of moist and dry air. Gymnasial Programtne^ So7i- 

 dersliausen^ 1874. 



ON THE RAINFALL AND EVAPORATION IN INDIA. 



In a memoir by A. R. Binnie on the Magpur water-works, 

 he gives some details with reference to the rainfall and the 

 drainage at Magpur. This city is situated in latitude 21 

 north, longitude 79 east, at an elevation of about 1000 feet 

 above the sea-level. The averagje rainfall for the nineteen 

 years from 1851 to 1873 was 40.7 inches, of which 37.5 inches 

 fell durinjT the monsoon months from June to the middle of 



o 



October. Although the general fluctuation of rainfall in 

 India is similar to that in other parts of the world, yet it has 

 certain well-marked peculiarities, the first of which is that 

 the greater part of the annual rainfall is confined to a few 

 months during the southwest or southeast monsoons; sec- 

 ond, the greater part of the year is almost rainless; and, third, 

 during the wet months the rainfall is much more intense than 

 in temperate countries. In the most violent showers that 

 have been noticed in that place the rain fell at the rate of 

 4.7 inches per hour. To determine the quantity evaporated 

 from the surface of the ground is a matter of difiiculty; but 

 Mr. Binnie attempted, by careful observation of the level of 

 the water in the receiving-basin during the dry season, and 

 by comparing the result with the existing meteorological 

 circumstances, to estimate the amount. During that period 

 in which no water ran into the basin, the quantity in the 

 latter diminished, in 242 days, to the extent of seven feet. 



