]90 CLIMATE. 



breaking and arresting the currents of air, which would 

 otherwise sweep through the forests ; and plains without 

 intervening rising grounds, high walls, or trees, arc fovour- 

 able to the diffusion of miasm, by allowing every slighS 

 horizontal motion of the air to intermix laterally the pure 

 and contaminated portions of it. Thick ranges ol trees, by 

 impeding this horizontal commixture when the an- is calm 

 or nearly so, and by altering the direction of light breezes, 

 are very etfectual in confining marsh-effluvia. That some 

 kinds of poisonous matters are produced by the decomposi- 

 tion of animal and vegetable substances seems highly prob- 

 able : others again may emanate from the interior ot the 

 earth as the result of subterranean action ; and these prob- 

 ably are the most noxious kinds. 



19. CZ?ma^c.— British India, situated partly in the torrid 

 and partly in the north temperate zone, is enclosed by 

 boundaries varying much in character,— namely, on the 

 west by the great Western Desert ; on the south-west, 

 south-east, and south by the ocean ; on the east by moun- 

 tain-ranges ; and on the north-east and north by the vast 

 alpine land of the Himmalehs,— a mountain-barrier so ele^ 

 vated as nearly to shut out the atmosphere of India, and 

 thus to secure a meteorological system for itself, different 

 from, and independent of that of Hindostan. As to form 

 and elevation above the sea, striking contrasts are displayed 

 between the flat lands of the Ganges, the mountain-chains 

 of the peninsula, the littoral plains of the Circars, and the 

 table-lands of Mysore. Its surface exhibits sandy deserts, 

 bare rocky plains, extensive cultivated fields, jungles, and 

 dense forests,— traversed by numerous and often consider- 

 able rivers, but rarely varied by the appearance of lakes ; 

 over which blows, for one half of the year, the south-west 

 monsoon, and during the other half the north-east mon- 

 soon, thus affording the conditions for a strikingly-marked 

 climate. The year is divided by the Hindoos into six sea- 

 sons, but the more common division is into three, viz. the 

 rainy, cold, and hot seasons ; the rainy in general extends 

 from June to October ; the cold from November to Febru- 

 ary ; and the hot from March to May. Every year there is 

 a variation in the commencement and termination of the 

 seasons, which renders absolute precision impossible in the 

 statement of them. The healthy season may be said to be 



