650 GLACIER-EROSION THEORY 



infinitely greater importance than the valleys either to the north or 

 south of the Alps ; but they were never connected with a lake. 



The question then arose, What was the physical reason of this great 

 difference between the tropical mountains and those of temperate 

 Europe? Nearly thirty years ago, he was for ten or twelve years 

 rambling about the Ilimalayahs along a stretch of 800 miles, and he 

 used to open a map before him, and try to make out the comparative 

 features of European and Eastern mountains. He looked to the 

 numerous lakes to the north and south of the Alps ; and he would put 

 the map of India alongside, where the same kind of rivers were de- 

 bouching into the plains, but where there was an utter absence of lakes 

 in connection with them ; and he used to puzzle himself in trying to 

 discover a physical explanation of this difference. He was perfectly 

 satisfied there must be some secondary conditions Avhich were not 

 common to the two, and he determined that, on his return to Europe, 

 he should make them the subject of special research ; for at that time 

 the glacial investigations of Charpentier and Agassiz in the Alps were 

 unknown to a solitary wanderer in the Ilimalayahs. That intention he 

 had carried out, by repeated visits to the Italian valleys of the Alps. 

 There was the same kind of elevation above the level of the sea, the 

 same kind of valleys, the same kind of fissures intersecting the great 

 ridges — What then was the explanation ? This he would endeavour 

 to indicate. About two years ago, March 5, 1862, as his friend Sir 

 Roderick Murchison was aware, a paper was brought before the Geo- 

 logical Society of London by Professor Ramsay, which excited a great 

 deal of attention, and gave rise to a very animated discussion. The 

 theory of the paper was that, as a rule, lakes in all the temperate and 

 cold regions of the world were the product of glacial excavation ; that 

 is to say, that wherever a glacier descended from a high ridge of moun- 

 tains into a plain, it ploughed its way down into the solid rocks and 

 carved out a great lake. This was the theory, or rather hypothesis 

 which Professor Ramsay pxrt forward, to explain the lakes which were 

 so abundant in the valleys of the Alps. A similar speculation, but 

 greatly more restricted, had been advanced by Mortillet a short time 

 before. He limited the action of the glacier to scouring out the silt of 

 the filled-up lake basins, the origin of which he attributed to antecedent 

 fissures the result of upheavement. An application of this theory was 

 made to the different physical phenomena which were connected with 

 the case ; and it occurred to himself and many others (and he believed 

 Sir Roderick had an opinion in common with himself), that it was not 

 adequate to explain the phenomena ; and on the occasion when it was 

 produced, he met it with the most lively opposition in connection with 

 his own experience in the Himalayan Mountains. The oj^position 

 which he gave to it was upon these grounds. Many of them would 

 remember that the lakes Maggiore and Como were upon the edge of the 

 plains of Italy ; that the glaciers, say that of the Ticino which came 

 down into the Lago Maggiore, descended along a steep incline, and 

 were at last delivered into that lake, which was about fifty miles long, 

 and only eight or nine miles wide at its widest point. Its prolongation 

 nearest to the Mediterranean attained a depth of about 2, GOO feet below 

 the level of the sea. Where the river escaped out of the lake it was 

 not more than about 600 feet above the level of the sea. It was a 



