DARWIN'S LETTERS TO HIS FRIENDS 49 



away from it. 1 A careful study of the two recent 

 volumes of Darwin's letters, and a re-study of the three 

 earlier volumes, with a view to this Address, have shown 

 how the writer's thoughts were again and again occupied 

 upon subjects bound up with the problem I have ventured 

 to bring before you this evening. The interest reaches 

 its height when we find that strongly marked differences 

 of opinion on fundamental questions are threshed out in 

 the correspondence, when we see, as I shall have occasion 

 to point out in greater detail in the later pages of this 

 Address, Darwin differing sharply from Huxley on the 

 one hand, and with Wallace on the other, as to the 

 significance and history of sterility between species. 



In such episodes we are permitted to become the 

 witnesses of a supremely interesting struggle, where 

 the central figure of modern biological inquiry is contend- 

 ing with his chief comrades in the great fight, with the 

 co-discoverer of Natural Selection, with the warrior hero 

 who stood in the forefront of the battle. 



The correspondence of Charles Darwin has a further 

 deep interest for us. We see the means by which 

 a gentle, sympathetic, intensely human nature overpassed 

 the stern limits imposed by health, and was able to impart 

 and to receive fresh ideas, and a stimulus ever renewed 

 the impulse to varied and unceasing research. I have 

 lately been studying with keen interest the life of another 

 great Englishman, William John Burchell, 2 than whom 

 no better equipped or more learned traveller ever explored 

 large areas in two continents. When I state that search- 

 ing inquiry has only brought to light a dozen of his 

 letters, 3 and that he was known to few of the great 

 naturalists of his day, we see the reason for the sad, 

 unproductive, brooding close of a career which opened 



1 Quarterly Review, January 1901, p. 258. 



a Ann. and Mag. Nat. Hist., January 1904, p. 45. 



8 Since these words were written I have through the courtesy of 

 Mr. Francis A. Burchell of the Rhodes University College, Grahamstown, 

 been permitted to see a large number of letters written by the great 

 explorer to members of his family. A number of Burchell's letters to 

 Swainson, of which I was unaware when this Address was written, are 

 preserved in the library of the Linnean Society. 



