268 XATATORES. 



must be convinced that the land is really the least productive 

 portion of the globe : and that the sea, taking its breadth, 

 its depth, and the energy of the powers that are in it, into 

 consideration, is more rich in proportion to the dry land, 

 than the valley of the Nile is in proportion to the adjoining 

 wastes of sand. The same, though in an inferior degree, may 

 be said of the permanent accumulations of fresh water 

 those that are inhabited generally by a few, and visited occa- 

 sionally by a few more, of the swimming birds. They not 

 only nourish a vast number of small animals in the water 

 itself, but they fertilize the banks, and render them produc- 

 tive of animals as well as of plants. Therefore, taking the 

 whole of the swimming birds, we may say that they are 

 more abundantly and securely provided for than any others 

 of the feathered tribes. They are also more free from casual- 

 ties ; for among sea birds there are few preyers predatory 

 quadrupeds there are, of course, none ; and though in the 

 lakes and rivers, some of the more voracious fishes do capture 

 a bird now and then, the number so captured is small there, 

 and there is seldom any such capture on the high seas. 



Natural powers are always so much in excess in propor- 

 tion to the scope that there is for their operation, that they 

 instantly supply any blank that may be occasioned by what, 

 because we know not its cause, we call contingency. But 

 still there is no waste ; and there is an exact proportion 

 between the energy of the powers and the average necessity 

 that there is for their operation. Accordingly, as the sea 

 birds are subject to fewer contingencies, their broods are less 

 numerous in proportion. Those which dabble on the shores 

 are exposed to more foes and contingencies. The common 

 teal has as many as twelve in a brood, and the common wild 

 duck eighteen. These breed on the margins of fresh-water 

 lakes, in countries rather temperate, and where there are 

 many destroyers. The fulmar petrel, which nestles in the 



