DARWIN'S NATURAL SELECTION 41 



and father-in-law, Josiah Wedgwood, sug- 

 gested to him that the apparent sinking of 

 stones on the surface might really be due to 

 earthworm castings. So, as soon as he had 

 some land of his own to experiment upon, he 

 began in 1842, to spread broken chalk over a 

 field at Down, in which, twenty-nine years 

 later in 1871, a trench was dug to test the 

 results. "What other naturalist," asks Allen, 

 ever waited so long and so patiently to dis- 

 cover the upshot of a single experiment? Is 

 it wonderful that a man who worked like that 

 should succeed, not by faith but by logical 

 power, in removing mountains?'' 



Darwin studied domestic animals. He ob- 

 served how many, and how widely different, 

 races there are of horses, dogs, swine, poultry 

 in general and pigeons in particular. In each 

 instance the many varieties are derived from 

 an original common stock, as domestic fowls 

 from the Indian jungle fowl, and pigeons from 

 the old-world rock-dove. 



''Derived," but how — by what process? In 

 the case of domestic creatures this was not 

 difficult to answer. It is accomplished by 

 breeders "selecting" the individuals to be bred 

 froir. In the case of pigeons, which Darwin 

 laid particular stress on the fancier seemed to 



