MAN AND NATURE. 301 



cially, has been brought about by animals far below 

 him in the scale of being ; which, unconsciously and 

 sometimes injuriously to themselves, have carried the 

 seeds and germs of life from one region to another. 

 What they have done by the mere instincts or acci- 

 dents of existence human intelligence has effected with 

 special interests and larger power. The record of 

 such exchanges would in itself fill a volume. We can 

 notice only a few of the more striking instances. 



The most remarkable, doubtless, is that which has 

 taken place between the continents of the Old World 

 and those across the Atlantic, which, though peopled 

 before, and by some semi-civilised races, yet came to 

 us as the discovery and conquest of a new world. 

 The balance of exchange here, as might be expected, 

 has been signally in favour of the latter. Even those 

 four articles cotton, sugar, rice, and coffee the ex- 

 port of which from America forms so large a part of 

 the commerce of the globe, are all derived from plants 

 originally carried thither by Europeans, and readily 

 propagated, where such diversity and extent of virgin 

 land was offered to their growth. To these more 

 tropical plants must be added the different varieties of 

 cereal grain, hemp, flax, clover, and other herbage, 

 now as thoroughly acclimatised in America as in 

 Europe. We have to set down something, however, 

 to the other side of the account. Of vegetable pro- 

 ducts America has given to the Old World the potato, 

 tobacco, and maize, besides several others of lesser 

 value. Looking singly to that remarkable root, the 

 potato, how r great has been its influence, as an article 



