GLACIAL EROSION' AND TRANSPORTATION. 269 



of the basins observed in the high Sierra, it seems evident that 

 the theory of the formation of rock-basins proposed by A. C. 

 Ramsay, from evidence obtained in Scotland and Switzerland, 

 is substantially correct, and furnishes the true explanation of 

 the origin of the examples before us.* The manner in which 

 the power of moving ice is directed so as to erode depressions 

 may be open to discussion, but the conclusion that rock-basins 

 are a result of glacial action is now too strongly supported by 

 facts to be questioned. . . . 



On examining the numerous lakes more critically, one finds 

 that many of them occupy depressions in morainal debris, or 

 are confined by terminal moraines. In numerous instances, 

 however, as in Bloody and Gibbs Canons, at the head of Rush 

 Creek, and all about Mount Lyell and Mount Ritter, the fact 

 that the lakes occupy depressions in solid rock is beyond all 

 question, One may walk entirely around many of them with- 

 out stepping off rock in place. . . . 



As some writers — especially those who are given to solving 

 the mysteries of Nature from their closets — have thought that 

 lakes filling true rock-basins are a rarity, and have even doubt- 

 ed whether they exist at all, we shall be interested in examin- 

 ing this result of glacial action, while we wait for our mule- 

 train to join us. The stream from above cascades over hun- 

 dreds of feet of rock before reaching the lake ; on either hand 

 the overshadowing cliffs tower upward for a thousand feet ; 

 and we can walk along the lower border of the lake and find 

 solid rock all the way across the canon. There is no doubt, 

 therefore, that the lake occupies a basin in solid rock. The 

 led^e confining the waters rises in places almost perpendicu- 

 larly to the height of over a hundred feet above the lake sur- 

 face, and indicates by its rounded contour and polished and 

 striated sides that the ice was once forced up from the basin, 

 now filled with water, and flowed over the ledges and down the 

 gorge. The sounding-line tells us that the bottom of the 

 basin is fifty-one feet below the lake surface. We thus have 

 a rock-basin of considerable depth, in the path of a glacier, 



* " On the Glacial Origin of Certain Lakes," etc., " Quarterly Journal of the 

 Geological Society of London,*' vol. xviii, 1862, pp. 185-204. 



