THE ORIGIN OF LAKES. 41 



which are due to irregular accumulations of drift, and 

 which are generally quite shallow ; (2) those which 

 are formed by moraines ; and (3) those which occupy 

 true basins scooped by glacier-ice out of the solid rock. 

 To the latter class belong, in his opinion, most of the 

 great Swiss and Italian lakes. Professor Ramsay 

 attributes their excavation to glaciers, because it is of 

 course obvious that rivers cannot make basin-shaped 

 hollows surrounded by rock on all sides. Xow the 

 Lake of Geneva, 1,230 feet above the sea, is 984 feet 

 deep, the Lake of Brienz is 1,850 feet above the sea, 

 and 2,000 feet deep, so that its bottom is really below 

 the sea-level. The Italian lakes are even more remark- 

 able. The Lake of Como, 700 feet above the sea, is 1,929 

 feet deep. Lago Maggiore, 685 feet above the sea, is 

 no less than 2,625 feet deep. It will be observed that 

 these lakes, like many others in mountain regions 

 those of Scandinavia, for instance lie in the direct 

 channels of the great old glaciers. If the mind is at 

 first staggered at the magnitude of the scale, we must 

 remember that the ice which scooped out the valley in 

 which the Lake of Geneva now reposes, was once at 

 least 2,700 feet thick ; while the moraines were also of 

 gigantic magnitude, that of Ivrea, for instance, being no 

 less than 1,500 feet in height. Professor Ramsay's 

 theory seems, therefore, to account beautifully for a 

 large number of interesting facts. 



The problem is, however, very complex ; and, while 

 admitting the force of Professor Ramsay's arguments, 

 there are, no doubt, other causes which have exercised 

 a considerable influence in the arrangement and con- 

 figuration of lakes ; for instance as has been ably 



