'^'28 The Afnerican Geologist. November, 1897 
species. In the beaches connected with the southern outlet a single 
species has been found, Unio ellipsis Lea, a common species of the 
upper Mississippi region. The remainder are found in a beach con- 
nected with a northeastern outlet. The scarcity of life in this lake 
may support the view of brief duration, though the coldness of the 
waters was probably influential in checking the spread of molluscan life. 
There appears to have been a general absence of life in other glacial 
lakes of the northern United States and Canada throughout most of 
their existence. As yet it is not known that any of them became well 
stocked with life until glacial conditions had ceased their influence. 
About 200 pages are devoted to a detailed description of the shores 
of lake Agassiz, embracing the author's work and additional data 
furnished by Mr. J. B. Tyrrell, of the Canadian survey. These des- 
criptions are accompanied by a series of maps which set forth the dis- 
tribution and relations of the beaches very clearly. The monograph 
throughout is well illustrated by maps, views and diagrams. 
In addition to the discussion of the history of this region a compre- 
hensive statement concerning its economic resources is presented. 
Sixty pages are devoted to the artesian and common wells of the Red 
river valley, and analyses of their waters. The use of artesian water 
for irrigation is briefly discussed. The agricultural resources of this 
far famed wheat belt are given forty-two pages and the geological re- 
sources which are rather meager are given eight pages. There are two 
appendices, one presenting a table of glacial striae, the other notes con- 
cerning the aboriginal earthworks found within and near the area of 
lake Agassiz. f. l. 
The Glacial Brick Clays of Rhode Island and. southeastern Massa- 
chusetts. By N. S. Shaler, J. B. Woodworth, and C. F. Marbut, 
(From the Seventeenth Annual Report. U. S. Geol. Survey, for 1895-96. 
Part I, pp. 951-1004, with two plates and ten figures in the text : Wash- 
ington, 1896.) The average thickness of the till in eastern Massachu- 
setts is estimated about 15 to 20 feet, and the proportion of its material 
which has the same character as the stratified clays and finely pulver- 
ized rock flour forming the beds described in this report is thought to 
be only about ten per cent. Therefore the extensive and thick beds of 
fine stratified drift found at low levels, and chiefly northward at the 
mouths of valleys, from New Jersey to Nova Scotia, derived from the 
glacial erosion, are regarded as proof that the North American ice- 
sheet, like the glaciers of Switzerland, discharged far more of its fine 
drift by subglacial streams than the part which remained in the mo- 
raines and general sheet of till. From the absence of ripple marks and 
current bedding, Prof. Shaler infers that the coast was depressed sev- 
eral hundred feet, being covered to that extent by the sea adjoining the 
receding ice-front, when these clays were deposited. 
The geological sequence and geographical distribution of the clay beds 
of this region are described by Mr. Woodworth, with a careful discus- 
sion of the time relations of the glacial and stratified drift formations 
in Nantucket, Martha's Vineyard, and Block island, and on the main- 
