UPPER INDIA. 81 



The heat and aridity of the climate of Upper India, so far as 

 they are due to bare plains and the hardness of the soil of the 

 country, will diminish in proportion to the increase of forests 

 and vegetation, and deeper cultivation and loosening of the 

 soil; or, in other words, the heat arising from the non- 

 absorptive and non-radiative state of the surface of the 

 country will not be produced and -cannot exist when it is 

 made absorptive and radiative. The second cause of the 

 excessive heat and aridity of the hot weather of the plains 

 of Upper India is surface - drainage ; and surface-drainage 

 is due to two sets of causes, the one natural and the other 

 artificial. 



The natural causes of surface- drain age, such as the gradual 

 formation of streams and valleys and the wearing away or 

 degradation of the surface by the action of rain, are laid down 

 in any standard work on physical geography or geology, and 

 these may be passed over with the remark that in former days, 

 when the population of any country was scanty, and when 

 more land remained covered with forest growth, and less land 

 had been brought under cultivation, more of the rainfall would 

 have been arrested by the earth and less would have found its 

 way by surf ace -drainage to the streams and rivers, which 

 probably in those days were confined in well-defined channels, 

 and were amply capacious to convey to the sea the amount of 

 water which found its way to them without flooding the land 

 near them. Forests and woods preserve moisture in a country 

 in so far as they prevent or retard surface-drainage by their 

 leaves, which fall and form a soft porous carpet on the surface ; 

 this yearly increasing in depth holds water like a sponge, 

 the lower layers gradually rot and become incorporated with 

 the soil ; thus, in the course of time, there is in every forest 

 (where not carried away by surface- drainage), above the mineral 

 soil a layer of loose humus, the remains of decayed leaves, on 



