228 Scientific Intelligence. 



miles northward from their native bed, and may I _ 

 mulation of sand moved by aqueous agencies quite inadequate to 

 move cubic yards of solid rock. I think that ice floes are capable 

 of such work ; and I believe it is not essentially different from work 

 in progress in the tracks of Arctic currents in modern times. 



The same agency would have picked up and transported the 

 rounded northern bowlders, which we find scattered, also, to some 

 extent, through the same sands. 



It could not be expected that the existing configuration of the 

 surface of the State should preserve the features which determined 

 the existence and boundaries of such local lakes as I have supposed; 

 but, after all, are not our existing interior lakelets examples of the 

 same, perpetuated by the delayed erosions of outlets ? If it be as- 

 serted that neither the less nor the greater lakes are engaged in 

 transportation of limestone masses, in our times, it will be a suffi- 

 cient rejoinder to remind the reader that the supply of movable 

 masses of limestone must ultimately have become exhausted. Still, 

 it is not a fact that work of this kind has entirely ceased, as any one 

 familiar with the flotsam thrown upon a lake beach will be led to 



ration, which in Southern Michiga 

 float toward the north. Between Saginaw Bay and the mouth of 

 the Grand River is a broad depression, the highest part, of which 

 rises but 12 feet above Lake Michigan. The southern tier of coun- 

 ties in the State presents an elevation of 300 to 600 feet above Lake 

 Michigan, The Corniferous limestone barrier, passing through 

 Monroe and Lenawee counties, still maintains an elevation of 100 

 to 150 feet above the same lake. Have we not here some vestiges 

 of that ancient conformation of the surface which resulted in a north- 

 ward drainage into the great channel once intersecting the State, 

 and the northward transposition of ice-born sheets of limestone and 

 sandstone, wrenched from the elevated barriers in Hillsdale, Lena- 

 wee and Monroe counties, and the contiguous portions of Ohio and 



2. On the outlet of the Great Salt Lake ; by Professor G. K. 

 Gilbert. (Letter to J. D. Dana, dated Washington, Feb. 4, 1876.)— 

 I had not seen Mr. Packard's paper, when my attention was called 

 to it by your letter of the 29th ult. Since he had " not observed 

 personally any facts bearing on the subject," but merely advanced 

 the ideas of others, it is not surprising that everything which is 



When the water of Great Salt Lake was at its maximum alti- 

 tude it carved and molded a beach, which yet remains— a con- 

 spicuous monument to its former greatness. Within the circle of 

 this beach-line are included also Utah and Sevier lakes. The 

 level of the ancient beach is 970 feet higher than Great Salt Lake, 

 about 700 feet higher than Utah lake, and about 550 feet higher 

 than Sevier Lake. From the upper beach the water slowly sub- 

 sided by desiccation, recording its lingeiings in a series of fointer 



