42 THE POPULAR SCIENCE MONTHLY. 



relation to the form and slope of the valleys and the intensity of 

 the glaciation to which they have been subject. In our own coun- 

 try we have in Wales a small number of valley lakes; in the 

 Lake District, where the ice-sheet can be proved to have been 

 much thicker and to have lasted longer, we have more numerous, 

 larger, and deeper lakes ; and in Scotland, still more severely gla- 

 ciated, the lakes are yet more numerous, many of those in the 

 west opening out to the sea and forming the lochs and sounds of 

 the western Highlands. Coming to Switzerland, which, as we 

 have seen, bears indications of glaciation on a most gigantic 

 scale, we find a grand series of valley lakes both on the north and 

 south, situated for the most part in the tracks of. those enormous 

 glaciers whose former existence and great development are clearly 

 proved by the vast moraines of northern Italy and the traveled 

 blocks of Switzerland and France. In Scandinavia, where the 

 Ice age reigned longest and with greatest power, lakes abound in 

 almost all the valleys of the eastern slope, while on the west the 

 fiords or submerged lakes are equally characteristic. 



In North America, to the south of the St. Lawrence River and 

 of Lakes Ontario and Erie, there are numbers of true valley lakes, 

 as there are also in Canada, besides innumerable others scattered 

 over the open country, especially in the north, where the ice-sheet 

 must have been thickest and have lingered longest. And in the 

 southern hemisphere we have, in New Zealand, a reproduction of 

 these phenomena a grand mountain range with existing glaciers, 

 indications that these glaciers were recently much more extensive, 

 a series of fine valley lakes forming a true lake district, rivaling 

 that of Switzerland in extent and beauty, with fiords on the south- 

 west coast comparable with those of Norway. 



Besides these valley lakes there are two other kinds of lakes 

 always found in strongly glaciated regions. These are Alpine 

 tarns small lakes occurring at high elevations and very often at 

 the heads of valleys under lofty precipices ; and small or large 

 plateau or low-level lakes which occur literally by thousands in 

 northern Canada, in Sweden, Finland, Lapland, and northwestern 

 Russia. The valley lakes and the Alpine tarns are admitted by all 

 geologists to be mostly true rock basins, while the plateau and 

 low-country lakes are many of them hollows in the drift with 

 which much of the country is covered, though rock basins are also 

 not infrequent. 



Here, then, we see a remarkable association of lakes of various 

 kinds with highly glaciated regions. The question is whether 

 there is any relation of cause and effect in the association ; and 

 to determine this we must take a rapid survey of other moun- 

 tain regions where indications of ice action are comparative- 

 ly slight or altogether wanting, and see whether similar lakes 



