UPPER INDIA. 19 



that we have increased its reflective and retentive properties, 

 and reduced its powers of absorption and radiation. This oper- 

 ation is performed every day in brickmaking. We have only 

 to compare the reflective and retentive powers of sun-dried 

 bricks with those of the loose earth from which they were 

 made, and we shall find they have increased in proportion to 

 the increased density of the materials composing them and 

 the smoothness of their surfaces, and have lost in the same 

 proportion their powers of absorption and radiation. 



Irrigation is a somewhat analogous operation. By it the 

 whole surface-soil is brought into the condition of sun-dried 

 bricks j the more water that has been applied to the land the 

 harder the soil becomes, and while its powers of absorption 

 and radiation are reduced, those of reflection and retention 

 of heat are increased ; and we also find that the power of 

 capillary attraction possessed by the land is increased, and 

 that the soil so compacted will sooner become dried up than 

 soil left loose and open, partly from the fact of the interstices 

 between its particles having been reduced in size, thus in- 

 creasing its capillarity, and partly from the increased heat of 

 the surface. Notwithstanding this, the advocates of irrigation, 

 while allowing that the heat of Upper India has increased of 

 late years, deny that irrigation has had anything to do with 

 causing the increased heat. I do not know how they can set 

 aside these ordinary laws of nature, perhaps they may be 

 able to explain how it is to be done. 



The soil of every field becomes somewhat caked on the 

 surface during the growth of a crop on it, from the effects of 

 any rain, or the dew which may drop from the crop upon it, 

 and becomes hardened and dries up, from the combined 

 effects of direct evaporation from the surface of the soil and 

 the secondary effects of the evaporation from the leaves of 

 the crop of the moisture which it had taken up by its roots. 



c 2 



