VI 



but his fertility in this respect was balanced by the 

 power of severe criticism to which he subjected the 

 products of his imagination. His son says that he was 

 willing to test what would seem to most people not at 

 all worth testing ; and that he enjoyed making what 

 he called " fools' experiments " to judge whether a 

 view or hypothesis was false or true. 



In science, however, the value of the imagination 

 increases with breadth of knowledge. A child may 

 imagine the stars to be windows in the vault of heaven, 

 and their twinkling the fluttering of angels' wings 

 passing in front of them. His conception of the stellar 

 universe may be beautiful, but it differs widely from 

 that on which the astronomer endeavours to construct a 

 scientific cosmogony. 



How easy it is to overlook objects and phenomena 

 when their significance is not understood is illustrated 

 by an incident related by Darwin himself. While a 

 student at Cambridge, he went to Wales with Sedgwick, 

 the professor of geology, and examined the rocks for 

 fossils. This was before Agassiz had shown that at one 

 period of geological history the rocks of the country 

 must have been buried beneath a sheet of ice which 

 left unmistakable marks of its action upon them. 

 " But," says Darwin, " neither of us saw a trace of the 

 wonderful glacial phenomena all around us ; we did 

 not notice plainly scored rocks, the perched boulders, 

 the lateral and terminal moraines. Yet these pheno- 

 mena are so conspicuous that, as I declared in a paper 

 published many years afterwards in the Philosophical 

 Magazine, a house burnt down by fire did not tell its 

 story more plainly than did this valley." 



Imaginative writers may produce fantastic romances 

 in which future conditions are portrayed, but neither 



