234 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



Ramsay then wrote a general paper " On the Glacial Origin of 

 certain Lakes in Switzerland, the Black Forest, Great Britain, 

 Sweden, North America, and elsewhere" (Q. 'Jour, GeoL Soc., 

 1862). In this paper Ramsay attributed the excavation of 

 many lakes and fiords to the erosive force of moving ice, and 

 Tyndall in the same year gave his opinion that the Alpine 

 valleys had been excavated by the same agency. 



During the forty years that have elapsed since that time the 

 erosive force of ice has been a subject of animated discussion, 

 and still there are two distinct parties amongst glacialists, 

 those who oppose and those who support the main issues of 

 Ramsay's discourses. Amongst the supporters or extreme 

 glacialists may be counted in Great Britain such geologists of 

 authority as Sir Archibald Geikie and Professor James 

 Geikie; in Austria, the geographer and geologist, Professor 

 Penck; in Switzerland, Professor Briickner; in Scandinavia, 

 Professor Nansen ; while in North America Sir William Logan 

 was a warm supporter. 



Geologists who oppose the extreme view of glacial erosion 

 have pointed out that a variety of local causes may give origin 

 to lakes and fiords. Actual cases have been cited where 

 fluviatile, or morainic accumulations, or, crust movements 

 would sufficiently explain the form of the basins attributed 

 to ice erosion. 



Much has been written in physics upon the causes of ice 

 movement. Of great importance were the experiments made 

 by Carnot and James Thomson (1849) on the liquefaction of 

 ice under strong pressure, and the lowering of the melting 

 point below o, as well as the discovery made by Faraday 

 (1850) of the re-union or regelation of fragments of ice with 

 moist surfaces. Application of the principle of fragmentation 

 and regelation to the phenomena of glaciers was made by the 

 leading physicists of the day, Tyndall (1857), Helmholtz 

 (1865), and Lord Kelvin, and thus a scientific explanation 

 was secured for the theory of glacier motion which had been 

 originally advanced by Rendu and Forbes. Professor Heim, 

 in his excellent Handbook of Glacier Phenomena (1885), 

 summarises the whole field of knowledge of Alpine glaciers. 

 He decides the question of glacier motion in the main in 

 favour of Forbes's theory of plasticity, but he also recognises a 

 gliding movement of the whole mass under the influence of 

 gravity. 



