186 THE CANADIAN NATURALIST. [June 



with water, and the shores are once more plentifully supplied 

 with rain. 



Extensive drainage, although beneficial to the rapid growth of 

 plants and to the profit of the agriculturist, may also tend to 

 diminish the rain fall by robbing the springs of their supply and 

 by conducting the surface water more rapidly to the livers and to 

 the ocean. 



Those lauds near the sea over which the wind transports 

 the aqueous vapour there acquired are, as a general rule, the 

 most plentifully watered, while those distant from this source 

 receive less in amount ; these facts are fully borne out by 

 actual observations. And may not the diminished rain fall in 

 England be attributed in a great measure to the extensive 

 surface draining by drain-tiles and other methods which are 

 resorted to to promote the rapid growth and excessive yield of 

 grain and some of the other agricultural products ? 



It will be seen that rain increases with the temperature, from 

 the fact that hot air holds more water suspended than cold. The 

 humidity of the atmosphere attains its maximum at the sea 

 shore, and there tends to produce the greatest amount of 

 precipitation. These causes are always present, but in a modi- 

 fied degree, and frequent, though small, showers are the necessary 

 consequence ; heavy and violent rain storms are of rare occur- 

 rence there. 



In proportion as the mercurial column in the barometer falls, 

 there is more chance of rain being formed, inversely in countries 

 with a high Barometric pressure, such as on the 30th degree of 

 latitude, where there is very little rain. Such regions have a 

 tendency to become deserts. 



Variations of temperature and irregularities of climate increase 

 the showers of rain ; and the formation of the soil plays also an 

 important part in the production of rain, for ascending concave 

 surfaces of soil receive a maximum, more especially when exposed 

 to rainy winds, and more rain falls in looudrd than in hare 

 districts. 



It rarely or never rains on the coast of Peru, in the great 



Valley of the River Columbia, in that of the Colorado in North 



America, the Sahara in Africa, and the Desert of Gobi in 



Asia, while in Patagonia and Chiloe it rains almost every day. 



Days of rain are more numerous in high than in low latitudes. 



lu the region of Calmus it rains during a part of every day, 



