MODERN GEOLOGY 



notion to the attention of Louis Agassiz, who was 

 spending the summer in the Alps. Agassiz was scep- 

 tical at first, but soon became a convert. 



In 1840 Agassiz published a paper in which the re- 

 sults of his Alpine studies were elaborated. 



" Let us consider," he says, " those more considerable 

 changes to which glaciers are subject, or rather, the 

 immense extent which they had in the prehistoric 

 period. This former immense extension, greater than 

 any that tradition has preserved, is proved, in the case 

 of nearly every valley in the Alps, by facts which are 

 both many and well established. The study of these 

 facts is even easy if the student is looking out for 

 them, and if he will seize the least indication of their 

 presence; and, if it were a long time before they were 

 observed and connected with glacial action, it is be- 

 cause the evidences are often isolated and occur at 

 places more or less removed from the glacier which 

 originated them. If it be true that it is the preroga- 

 tive of the scientific observer to group in the field of his 

 mental vision those facts which appear to be without 

 connection to the vulgar herd, it is, above all, in such a 

 case as this that he is called upon to do so. I have 

 often compared these feeble effects, produced by the 

 glacial action of former ages, with the appearance of 

 the markings upon a lithographic stone, prepared for 

 the purpose of preservation, and upon which one 

 cannot see the lines of the draughtsman's work unless 

 it is known beforehand where and how to search for 

 them. 



44 The fact of the former existence of glaciers which 

 have now disappeared is proved by the survival of the 



147 



