DYNAMICAL GEOLOGY. 22Q 



time in the form of letters in the Edinburgh New Philosophical 

 Journal. He established the important fact that glaciers move 

 more rapidly in the middle than at the sides and bottom, 

 and argued from this differential motion that the glacier ice 

 behaved like a slightly viscous mass, which under the influence 

 of gravity was bound to flow slowly downward after the manner 

 of a lava stream. So many of the glacier phenomena were 

 explained by Forbes's theory of the plasticity of the ice, that it 

 immediately found wide acceptance. 



The Swiss botanist, Martins, explored glaciers in Spitz- 

 bergen and Scandinavia. He demonstrated the former greater 

 extent of the glaciers in those territories, and made the first 

 detailed study of " ground-moraines," and the kind of sedi- 

 ment deposited by the river out-flows from glaciers (glacial 

 diluvium). 



In all countries where science was cultivated rapid studies 

 were made between 1840 and 1850 in glacial geology; Great 

 Britain, the Pyrenees, the Black Forest, Upper Italy, Scandi- 

 navia, North America, were diligently and successfully searched 

 for evidences of an epoch of extensive glaciation. Germany 

 was much longer in accepting the new teaching. Leopold 

 von Buch strongly opposed the results attained by the Swiss 

 glacialists, and his influence retarded scientific inquiry of the 

 question in North Germany. 



The city of Munich enjoys exceptional natural advantages 

 of position for glacial research, seeing that the Bavarian plain 

 upon which it stands has been smoothed and scratched by the 

 ancient glaciers upon the Bavarian Alps and the Tyrol, and 

 the river Isar, which flows through Munich, gives immediate 

 access to the system of Alpine valleys formerly occupied by 

 these glaciers. The famous astronomer, Gruithuisen, had 

 published at Munich, in 1809, a paper on the erratic blocks of 

 the South Bavarian plain, wherein he stated that they had been 

 brought from the neighbouring Tyrolese and Bavarian Alps. 

 He advanced the idea that glaciers had transported them to 

 the low Alpine levels, and then the ice-masses in which the 

 erratics were wedged had been borne northward across the 

 plains by enormous floods, the same which had spread the 

 nagelflue conglomerates over the sub-Alpine Bavarian plain. 

 As the ice-masses melted, the erratics were left in their various 

 positions. This was in substance the conception adopted by 

 Karl Schimper several decades later. 



