542 



THE POPULAR SCIENCE MONTHLY. 



which fill rock-basins, with the rock-surface fresh from under the ice of 

 the Mer de Glace, we shall find them wonderfully similar in their mark- 

 ings. The characters that are engraved upon them are the same. 



Not only do we find these markings in connection with the present 

 glaciers, but we find also the rock-basins themselves with the glaciers 

 yet occupying their upper portions, and still at work grinding down 

 the rocks. The best example of this kind, perhaps, in the world, is 

 Lake Wakatipu, in New Zealand, which has a length of seventy 

 miles, and a depth of 1,400 feet. This lake fills a true rock-basin, and 

 bears every indication of having been excavated by the glaciers, 

 which in the past were greatly extended, and have now retreated to 

 the extreme upper end of the valley, while it has no connection with 

 synclinal folds or volcanic fractures. 



How can we resist the conclusion, then, that these bowlders, these 

 beds of clay full of smoothed and striated pebbles, and these rock- 

 basins with their sides covered with inscriptions which we can now 

 read with ease and accuracy if we take the records made by existing 

 glaciers, as the Rosetta Stone are all the work of glaciers, since the 

 same results are produced at the present day by the action of ice, 

 and by no other agency known ? 



A clearer idea of the manner in which a flowing glacier wears out 

 a rock-basin can be gathered, perhaps, from the accompanying dia- 

 gram, where the rock H H is shown, over which passes the glacier G, 



which wears its bottom less at the lower end, not only for the reason 

 that the ice is continually wasting away, and growing thinner in the 

 lower portion, but also because the material carried down on the sur- 

 face of the glacier is deposited at its extremity M, in the form of a 

 ternjinal moraine, and thus protects the rock beneath from further 

 waste. When the ice of the glacier is melted away, and the terminus 

 retreats up the valley, the basin which it leaves behind it becomes 

 filled with water (from Mto G), and thus forms a lake, which maybe 

 a mere pool across which a school-boy can skip a stone, a great inland 

 sea like Lake Erie or Lake Ontario, or a mirror of grandeur like Lake 

 Geneva or Lucerne, in Switzerland, and Lake Wakatipu and Lake 

 Wanaka, in New Zealand. 



