28 The Founders of Geology LECT. 



strated that fossil shells often have attached to them other 

 shells, and likewise barnacles and serpulae ; that many of 

 them have been bored into by other organisms, and that 

 in innumerable instances they are found in a fragmentary 

 and worn condition. In all these respects the beds of 

 fossil shells on the land are shown to present the closest 

 possible analogy to the floor of the present sea, so that it 

 becomes impossible to doubt that the accidents which have 

 affected the fossil organisms arose from precisely the same 

 causes as those of exactly the same nature that still befall 

 their successors on the existing ocean bottom. 



Of course nowadays such reasoning appears to us so 

 obvious as to involve no great credit to the writer who 

 elaborated it. But we must remember the state of natural 

 knowledge more than one hundred and thirty years ago. 

 As an example of the method of explaining and illustrating 

 the former condition of the earth's surface by what can be 

 seen to happen now, Guettard's memoir is unquestionably 

 one of the most illustrious in the literature of geology, 

 opening up, as it did, a new field in the investigation of 

 the history of our globe, and unfolding the method by 

 which this field had to be cultivated. 



On what is now known as Physiographical Geology, or 

 the discussion of the existing topography of the land, this 

 same illustrious Frenchman left the impress of his mind. 

 I will cite only one of his contributions to this subject 

 a memoir " On the Degradation of Mountains effected in 

 our Time by heavy Kains, Kivers and the Sea." 1 This 

 work, which occupies about 200 quarto pages, deals with 



1 See vol. iii. of his Memoires sur difffrentes parties des Sciences et des 

 Arts, pp. 209-403. 



