426 NINETEENTH CENTURY. PT. in. 



and on his return he wrote an account of the geology and 

 natural history of the countries he had visited. He tells us 

 himself that even so early as this he noticed many facts 

 which seemed to him to throw light on the difficult question 

 of the origin of the different species of plants and animals ; 

 and he spent twenty years carefully collecting in England all 

 the knowledge he could upon the subject. But he did not 

 publish it, for he wanted more and more evidence ; and as 

 Newton waited sixteen years for more convincing proof 

 before he announced his theory of gravitation, so Mr. Dar- 

 win would have delayed much longer than he did if a 

 remarkable circumstance had not obliged him to speak. 



It happened that while Mr. Darwin was working in Eng- 

 land, another great naturalist, Mr. Alfred R. Wallace, who 

 was then in the Malay Archipelago, also thought that he 

 had discovered the way in which animals are made to vary 

 in the course of long ages. He sent home a paper on the 

 subject, and, though he had never heard of Mr. Darwin's 

 theory, it was found that he had worked out the same 

 result, sometimes almost in the same words. 



Sir C. Lyell and Dr. Hooker of Kew were so much struck 

 with the fact that these two men had solved the problem 

 almost precisely in the same way, that they begged Mr. 

 Darwin to allow one of his papers, written many years 

 before, to be published with Mr. Wallace's, and the two 

 essays were read the same evening, July i, 1858, at the 

 Linnaean Society. A year later, in November 1859, Mr. Dar- 

 win's famous work, ' The Origin of Species,' was published. 



' The Theory of Natural Selection,' or the choosing out 

 by natural causes of those plants and animals which are 

 best fitted to live and multiply, rests upon a few simple facts 

 which you can understand. 



