INTRODUCTION. 3 



to the refreshment and the productiveness of all around 

 them. In countries which are uncultivated the wea- 

 ther is mostly in extremes. Rain, when it comes, 

 takes the form of an overwhelming flood, not gently 

 entering into and moistening the soil, but rushing 

 along the surface, tearing up one place, strewing 

 another with the debris, and reducing both to a state 

 of indiscriminate ruin; while scarcely has the flood 

 gone by, when the returning heat evaporates the little 

 moisture which is left behind, and burns up the 

 coarse and scanty vegetation which the rains had 

 fostered. 



These effects of the unmitigated action of the ele- 

 ments are most strongly marked in those parts of 

 the world where hitherto the seasons have defied the 

 labour of man, and have seemed to wage war upon 

 his agriculture. This is the case in some parts of 

 India, in Southern Africa, and in a great part of what 

 we yet know of Australia, where at one time the earth 

 is parched up, and the beds of rivers become dry 

 channels or unconnected pools, while at another they 

 suddenly pour onward to the sea in a wide spreading 

 inundation, or roll their rapid floods in narrow but 

 deepened channels. That the labours of cultivation 

 exert the most, beneficial effect upon climate may be 

 shown, by contrasting the waste and uncultivated 

 parts of our own country with other parts in the same 

 latitude, and at the same elevation above the level 

 of the sea. but which are in a state of high cultiva- 

 tion. In these, while the immediate object of pro- 

 viding a certain and abundant supply of food has" 

 been accomplished by the labours of man, an indi- 

 rect influence has been exerted scarcely less beneficial, 

 by rendering the country in general more healthy 

 and agreeable. 



In the central parts of Scotland, where the intro- 

 duction of agricultural improvements has been much 



