ON THE FORMATION OF LAKES. 



539 



ures developing by more or less rapid stages along a definite course 

 in the direction of the type of structure selected for our consideration 

 to-day, and, though I am ready to make an act of scientific faith in 

 the existence of such creatures, I confess my imagination fairly baffled 

 in its attempts to depict them, or the road which this particular course 

 of evolution followed. We must wait patiently for more light from 

 paleontology. But we may wait very hopefvdly. We may do so 

 because the wonderfully rich harvest of fossil remains now being 

 gathered in North America supplies us with good and solid ground 

 for hope. 



Already forms have been discovered there so strange that they 

 cannot be satisfactorily gi-ouped in any existing order of mammals 

 forms such as imagination could hardly have anticipated. We may, 

 then, not unreasonably expect that sooner or later perhaps very soon 

 fossils deeply buried in the secondary rocks will come to light, clearly 

 pointing out the line which has been followed in the evolution and 

 development of the only truly flying mammal the bat. Popular Sci- 

 ence Review. 







ON THE FORMATION OF LAKES. 



Br I. C. RUSSELL. 



IT was not until the studies of Agassiz, Forbes, and others, among 

 the Alps of Switzerland, had made us acquainted with the char- 

 acter and action of glaciers, that we could at all understand many of 

 the most curious and interesting features connected with the forma- 

 tion of the multitude of lakes with which we are more or less familiar, 

 and which lend so much beauty and grandeur to the scenery of the 

 world. 



As some classification is necessary for the understanding of a 

 series of facts, we will arrange lakes under four heads : 1. Those filling 

 glacier-worn rock-basins ; 2. Those confined by banks of sand, gravel, 

 bowlders, etc., or, in one word, by moraines ; 3. Those formed by a 

 subsidence of their bottoms, or by the elevation of the country sur- 

 rounding them, commonly by the secular changes of level to which 

 the crust of our globe is subject ; 4. Lakes filling basins formed by 

 volcanic action. 



1. Lakes which fill rock-basins are such as are confined on all 

 sides by the common rock of the country, so that in some cases a 

 person cau walk entirely around them without stepping off the solid 

 rock; and in all cases they would be found to have a rocky rim 

 inclosing them, were the superficial material removed. How such 

 spoon-shaped depressions could be scooped out, was for a long time 

 an enigma which eluded the search of the most painstaking observers. 



