THE GREAT ASIATIC STEPPE REGION. 45 



restrial surface. These form what we have ventured 

 to call "The Climatic Zones." Some of them are 

 marked with exceeding distinctness. Notably, for 

 example, " The Great Forest Region of the Equatorial 

 Zone," of which we have already spoken. Again, 

 take the prairie, or Steppe Region : see the vast ex- 

 tent of these treeless plains in North America, and 

 again in the same parallel of latitude, right across 

 the great continent of Asia, and across parts, at all 

 events, of that of Europe notably, for instance, in 

 Southern Russia. Then again these great plains re- 

 appear in a similar position in the southern hemisphere, 

 in the pampas of South America, and in the karroo 

 and grass veld of Southern Africa, though on account 

 of the great preponderance of ocean in that hemi- 

 sphere, their extent is very much smaller than in the 

 northern hemisphere. 



So we might go on to show that, save and except in 

 certain exceptional districts, the whole earth is thus 

 laid out substantially in a series of climatic bands or 

 zones throughout its entire terrestrial extent; and 

 again, wherever exceptional regions do extend, form- 

 ing a breach in their continuity, in almost every case 

 there are evident reasons which make it apparent why 

 they should occur where we find them. 



Moreover, these very exceptions to the general law 

 are in themselves in a pre-eminent degree suggestive 

 and instructive ; and show in terms that speak louder and 

 clearer than any words could do, that all these varia- 

 tions in the nature of a country depend upon climate. 

 The two great factors in climate, as we have said, 

 are heat and moisture. Where there is a damp at- 

 mosphere, the tendency is to produce arborescent 



