66 Physical Geography as a Popular Study. 



little farther, we shall see that the physical geography of Africa 

 has opposed difficulties to the advance of civilization which we 

 do not yet know how to overcome. In like manner immense 

 tracts of country on the borders of the Amazon cannot, from 

 considerations of physical geography, become the home of a 

 numerous and cultivated population, until gigantic means can 

 be employed to cut away its rampant vegetation, and drain its 

 enormous swamps. In dealing with Africa, the difficulties 

 are physical and moral, and the beneficent influence of the 

 European mind upon the African mind can only be exerted 

 successfully by a combination of powerful countries like En- 

 gland, America, and France, to compel the cessation of the 

 slave trade, and establish honest, commercial settlements at 

 the most convenient points. 



Professor Ansted has an interesting chapter on the efforts 

 of human agency in modifying the earth's surface, and there is 

 every reason to believe that, within a few generations, the 

 conditions of prodigious tracts of country will be greatly im- 

 proved. India is undergoing an enormous change, through 

 the restoration and extension of works of irrigation, and the 

 impulse given to cultivation by the augmentation of means of 

 transport. The slave states of America are passing from bar- 

 barism to civilization, and in a generation or two, millions of 

 educated men will replace millions brought up in a condition 

 little above that of domestic animals, swamps will be drained, 

 waste land reclaimed, barren land cultivated, and thus many 

 thousands of square miles will experience a considerable modi- 

 fication of climate as well as of aspect. When sandy wastes 

 are sufficiently near centres of civilization to be worth the cost 

 of modifying, we find them gradually converted into pasture 

 and forest. First, certain plants are grown which give stability 

 to the shifting mass, and other plants succeed them, and, in 

 time, trees with their power of attracting moisture and pro- 

 tecting the soil from evaporation, rear their heads. Even in 

 certain extensive deserts, it is believed that water for their fer- 

 tilization might be obtained by artesian wells, and the constant 

 demands of commerce for new markets and new routes of 

 transit, tend to bring into importance tracts of country that 

 have for ages been stationary, because the world's industry and 

 invention had left them alone. 



Apparently trifling circumstances may lead to considerable 

 changes, as when the accidental introduction of a new plant 

 or a new insect interferes with pre-existing arrangements and 

 modifies the vegetation of a country or a district, thereby 

 leading to changes in its supply of moisture, amount of eva- 

 poration, etc., etc. 



It iSj however, when civilization is most active, that man's 



