Geology. 455 



greater time previous, and a relatively much earlier determina- 

 tion of the composition and concentration of the " organic 

 medium." 



There has also just appeared a bulletin of the Illinois Geologi- 

 cal Survey on the waters of the East St. Louis district,* which 

 should be studied at the same time. The Mascoutah well seems 

 to be especially of interest. Unfortunately there are a number 

 of slips by which contradictory statements as to the character of 

 the water at different depths are made, but it seems likely that 

 there are two main flows as usual, one from the Carboniferous 

 and one from the Calciferous, differing greatly in sodium. In 

 chlorine and total solids it asrrees with the strongest of the Mis- 

 souri water. 



2. The Falls of the Niagara, — their Evolution and varying 

 Relations to the Great Lakes; Characteristics of the Power, and 

 the Effects of its Diversion; by Joseph William Winthrop 

 Spencer. Pp. xxxi, 470, with 58 plates and 30 figures, frontis- 

 piece and map. Geological Survey of Canada, Ottawa, 1907. — 

 During the years 1905-1906 special surveys were made to deter- 

 mine disputed points regarding the origin and history of certain 

 features of the Niagara falls region. The results of these sur- 

 veys, taken in connection with work previously done by Spencer, 

 Taylor, Gilbert and others, give a fairly complete account of 

 the physiography of the Niagara river. New soundings have 

 been made for the entire gorge, which have determined its shape 

 much more accurately than heretofore. The soundings directly 

 underneath the Canadian falls, where an unexpected depth of 192 

 feet was found, and also in the Whirlpool rapids, were executed 

 with great skill. 



A detailed study of the form of the gorge in connection with 

 the structure of the rock forming its sides and bed has led to 

 recalculations of the rate of recession. The mean rate for the 

 Canadian falls from 1842 to 1905 is 4*2 feet annually; for the 

 American falls about *6 of a foot annually. The rate is slower 

 now than previously and the future retreat will be still slower, 

 owing to the fact that the river is now receding up the bank of 

 an ancient river depression. 



The chapters dealing with the development of the Great Lakes, 

 their shifting outlets due to uncovered channels and earth tilting, 

 contain material that has pi - eviously been presented, but for the 

 first time a definite pre-Glacial outlet for Lake Erie has been 

 discovered and the existence of a buried valley extending from 

 the falls south westward toward the Welland river has been 

 proven by well borings. A study of the rainfall, fluctuation of 

 level, amount of discharge, etc., of Lake Erie is discussed in 

 detail, and the conclusion reached that there has been practicall} r 

 no tilting of the lake beds during the past fifty years. 



* Bulletin No. 5. Illinois Geological Survey by I. Bowman and C. A. 

 Eeeds (this Journal, April, 1908, p. 393). The Mascoutah well is mentioned 

 pp. 24, 57, 64, 76, 78, 93, 94, 117. 



