PREGLA CIAL GRAVELS NEAR BARABOO, WIS. 667 
ridge, or at least that they were once at equally high points in 
the immediate vicinity. If these formations once covered the 
quartzite and were overlain by the Hudson River shale, the 
Niagara limestone, which, in Wisconsin, immediately succeeds the 
Hudson River shale, must have originally lain very high above 
the crest of the quartzite range. If the Trenton lay upon the 
quartzite directly, and if it and the succeeding Galena and 
Hudson River formations had their usual thickness, the base of 
the Niagara could hardly have been less than 500 feet above the 
the top of the east bluff at Devil’s Lake. If the St. Peters sand- 
stone and the lower Magnesian limestone overlay the quartzite 
beneath the Trenton, the base of the Niagara must have been 
still higher. 
R. D. SALISBURY. 
