44 HISTOBY OF THE SCIENCE. 



others, and having arrived at the conclusion, that the gla- 

 ciers of the Swiss Alps had formerly a greater extension, 

 and reached as far as Mount Jura, determined to investigate 

 the traces of glaciers in England, Scotland, and Ireland. 

 The existence at a former period of glaciers of far greater 

 importance and extent than those with which we are now 

 acquainted, covering, in fact, the whole of Switzerland, and 

 presenting an area of sixty leagues, with a surface of more 

 than two hundred square leagues, seems to have been com- 

 pletely and satisfactorily established by the researches of 

 M. Charpentier, whose testimony is of the more value, 

 because having at first been opposed to the theory, he 

 became, by the result of his inquiries, a convert. But though 

 the certainty of these vast fields of ice, in Switzerland and 

 its vicinity, seems to be thus demonstrated in a convincing 

 manner, it is by no means so clear that the same phenomena 

 existed in other and distant regions, and even if they did, it 

 is not considered that they account for the erratic blocks, 

 which we have already referred to another cause. M. Agassiz 

 conceives that the markings and striations of the rocks 

 observed in Great Britain, are similar to those occurring in 

 Switzerland, and testify the former prevalence of extensive 

 glaciers in these regions. He farther applies their agency 

 in explanation of many local phenomena; in particular, of 

 the erratic blocks, and of the parallel roads of Glenroy, which 

 are certain level terraces on the sides of mountains, pre- 

 viously supposed to be ancient sea-beaches left by the retiring 

 of the sea. His views have been warmly espoused by Dr. 

 Buckland and Sir C. Lyell, but have met with much opposi- 

 tion in Germany,* It must be admitted that they scarcely 

 account in a satisfactory manner for all the phenomena 

 which they are adduced to explain, in particular the parallel 

 roads above-mentioned ; Sir B. Murchison, on his recent visit 

 to Hussia, found them insufficient to explain the position of 

 the erratic blocks strewed over vast portions of that country.f 

 The late Mr. Bowman stated J the following objections to the 



* Particularly from Studer and Von Leonhard. See the admirable work of 

 the latter, Geologic oder Naturgeschichte der JSrde, auf A llgemeine fassliche 

 Wtise abgekandelt, p. 487, Stuttgart, 1840. 



f See Proceedings of the Geological Society, vol. iii. p. 405. 

 Philosophical Magazine. 



