V GLACIAL EROSION OF LAKE BASINS 99 



Equator, produce only a few small lakes on the high 

 plateaux, and a few in the great lowland river plains — 

 probably the sites of old river channels — but no valley 

 lakes in any way comparable with those of Switzerland or 

 even of our own insignificant mountains. 



Having thus roughly surveyed the chief mountain 

 regions of the whole world, we find that true subalpine 

 valley-lakes, that is, lakes in the lower parts of the valleys 

 descending from mountain ranges or groups, filling up 

 those valleys for a considerable distance, usually very deep, 

 and situated in true rock-basins — that such lakes as these 

 are absolutely unknown anywhere but in those mountain 

 regions which independent evidence shows to have been 

 subject to enormous and long-continued glaciation. No 

 writer that I am acquainted with has laid sufficient stress 

 on this really marvellous fact of lake-distribution. Pro- 

 fessor Bonney passes it by with the remark, that there is 

 a perfect gradation of lakes, from the smallest tarns to 

 those of North America and Central Africa ; and Mr. 

 Douglas Freshfield says, that, wherever on the surface of 

 our globe there are heights there must be hollows ; and 

 other writers think that lakes are general results of the 

 process of mountain-making. But none of these writers 

 have apparently even noticed the fact, that glacier valley- 

 lakes have a distinctive character which separates them 

 broadly from the lakes of all non-glaciated countries, and 

 that they are totally absent from such countries. 



But besides the mountains which possess true valley- 

 lakes, there are a number of ranges which have been 

 glaciated yet do not possess them, and this absence of 

 lakes has been used as an argument against the connection 

 of valley-lakes with glaciation. A little examination, 

 however, shows us that these cases greatly strengthen our 

 argument. Comparatively large and deep valley-lakes 

 are the result of excessive glaciation, which has occurred 

 only when conditions of latitude, altitude, and moisture 

 combined to produce it. In regions where glaciation was 

 of diminished intensity, from whatever causes, valley-lakes 

 diminish in size and number, till at last only tarns are 

 found in moderately glaciated districts. Thus, the 



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