246 THE POPULAR SCIENCE MONTHLY. 



It is, in fact, only on account of this powerful agency that we 

 do not find valley lakes abounding in every mountainous country, 

 since it is quite certain that earth movements of various kinds 

 must have been continually taking place. But if rivers have 

 always been able to keep their channels clear, during such move- 

 ments, among the mountains of the tropics and of all warm coun- 

 tries, some reason must be found for their inability to do so in the 

 Alps and in Scotland, in Cumberland, Wales, and southern New 

 Zealand ; and as no reason is alleged, or any proof offered, that 

 sufiBciently rapid and extensive earth movements actually did 

 occur in the subalpine valleys of these countries, we must decline 

 to accept such a hypothetical and unsatisfactory explanation. 



Nothing is more easy, and nothing seems at first sight more 

 plausible, than to allege these " earth movements " to account for 

 any one lake whose origin may be under discussion. But it ceases 

 to be either easy or plausible when we consider the great number 

 of the lakes to be accounted for, their remarkable positions and 

 groupings, and their great depths. We must postulate these 

 movements, all about the same time, in every part of the High- 

 lands of Scotland, everywhere in the Lake district, and on both 

 sides of the Alps. Then, again, the movements must have been 

 of greater extent just where we can prove the glaciation to have 

 been most severe. It produced lakes from one hundred feet to two 

 hundred and seventy feet deep in Cumberland and Westmore- 

 land ; in Scotland, where the ice was much thicker, the lakes are 

 from over three hundred to over one thousand feet deep ; while in 

 the Alps of Switzerland and North Italy, with its vast glaciers and 

 ice-sheets, many are over one thousand feet, and one reaches the 

 enormous depth of over twenty-five hundred feet. It may be said 

 that the depth is in proportion to the height of the mountains ; 

 but in equally high mountains that have not been glaciated there 

 are no lakes, so this can not be the true explanation. One more 

 remarkable coincidence must, however, be pointed out. The two 

 largest Swiss lakes those of Geneva and Constance are situated 

 just where the two greatest West European rivers, the Rhone and 

 the Rhine, get beyond the mountain ranges ; while on the south, 

 one of the largest and by far the deepest of the lakes Lake Mag- 

 giore collected into its basin the glacier streams from a hundred 

 miles of the high Alps, extending from Monte Rosa on the west 

 to the peaks above San Bernardino on the east. Throughout this 

 great curve of snowy peaks the streams converge, with an aver- 

 age length of only thirty miles, to unite in a valley only six hun- 

 dred and forty-six feet above the sea level. No such remarkable 

 concentration of valleys is to be found anywhere else in the Alps, 

 and no other lake reaches to nearly so great a depth. On the 

 theory of glacial erosion we have here cause and effect ; on that 



