57 



showing that the country was forested. To this succeeds wet 

 spongy peat as before, to be again covered with dry peaty soil 

 and tree-trunks, &c., and so on." 



Respecting the great precipitation of the glacial climate — 

 including in precipitation, of course, both rain- and snow-fall — 

 I take the following evidence from Professor Geikie's paper on 

 " The Geysers of the Yellowstone," in Macmillan 's Magazine, 

 May, 1881 : — 



The Great Salt Lake of Utah, North America, is 5,250 feet 

 above the sea, and is at present without outlet, and only 80 

 miles long by 52 broad. But at a height 940 feet above its 

 present surface, a terrace has been discovered which is without 

 doubt an ancient shore of the lake, and corresponds in height 

 with a gap in the rim of the lake-basin, by which the lake over- 

 flowed in a river which was a tributary of the Snake River or 

 Upper Columbia. An examination of the terrace shows that 

 the lake then extended 300 miles by 180, so that its area was 

 then, speaking roughly, about twenty times what it is now. 

 The moraines of ancient glaciers show that the glaciers which 

 produced them came down to the lake from the Wahsatch 

 mountains, which are only about 3,000 feet higher than its sur- 

 face at that time. Freshwater shells are found along the terrace, 

 but they are not needed to prove that a lake with an outlet 

 must have been of fresh water. 



We see from these facts that whereas the precipitation of 

 Salt Lake Basin is now carried off by the evaporation of the 

 Salt Lake, at a recent geological period, which was probably 

 the glacial, the precipitation of the same area filled a lake of 

 twenty times the extent, and was not all carried off by its eva- 

 poration, but part of it overflowed in a river. This proves 

 either that the quantity of precipitation must have been much 

 greater than now, or the force of evaporation much less ; — 

 probably both. 



