CHAPTER XV 



SCIENCE AND TRAVEL THE VOYAGE OF THE 



BEAGLE 



SIR CHARLES LYELL, in his Principles of Ge- 

 ology, the first edition of which appeared in 1830- 

 1833, says : " If it be true that delivery be the first, 

 second, and third requisite in a popular orator, it is 

 no less certain that travel is of first, second, and 

 third importance to those who desire to originate 

 just and comprehensive views concerning the struc- 

 ture of our globe." The value of travel to science 

 in general might very well be illustrated by Ly ell's 

 own career, his study of the mountainous regions of 

 France, his calculation of the recession of Niagara 

 Falls and of the sedimentary deposits of the Missis- 

 sippi, his observations of the coal formations of Nova 

 Scotia, and of the composition of the Great Dismal 

 Swamp of Virginia suggestive of the organic origin 

 of the carboniferous rocks. 



Although it is not with Lyell that we have here 

 principally to deal, it is not irrelevant to say that 

 the main purpose of his work was to show that all 

 past changes in the earth's crust are referable to 

 causes now in operation. Differing from Hutton as 

 to the part played in those changes by subterranean 

 heat, Lyell agreed with his forerunner in ascribing 

 geological transformations to "the slow agency of 

 existing causes." He was, in fact, the leader of the 

 uniformitarians and opposed those geologists who 



