Amount, of Water in the Earth''.s Crust. — Greenlee. 38 
zon must remain indeterminate between the limits of the Tren- 
ton and Niagara. 
The other locality to be mentioned is a few miles southeast 
of Deadwood, South Dakota, and was visited b}^ the writer in 
1889. Here a heavy bedded, yellow limestone occurs above 
the Cambrian and at some distance below the Carboniferous 
limestone. Fossils are not abundant, the only forms observed 
being a large annvilated orthoceratite and a large gastropod. 
Specimens of these were sent to Walcott by F. R. C'arpenter 
in 1891, and determined to be Emlocerds ((nnulatum and 
Maclurea lognni, and therefore indicative of Trenton age.* 
Examples of Holysites from this region led the writer to infer 
the presence of Niagara, and it was so recorded in the fourth 
edition of Dana's '• Manual of Geology," but, as in the pre- 
vious instance, recent investigations have shown the unreli- 
ability of several species generally considered as characteris- 
tic of the American Niagara, notwithstanding that in Europe 
the same forms are well known to have a wide vertical range. 
THE AMOUNT OF WATER IN THE EARTH'S 
CRUST. 
W. B. Greenlee, Ithaca, N. Y. 
In order to ascertain the amount of mechanically contained 
water in the earth's crust I recently made the following com- 
putation : 
I considered it safe to assume that tlie crust of the earth is 
tilled with water and that the maximum porosity of rocks 
which can be obtained in the laboratory, though not the 
greatest possible porosity, is less than that of the crust of the 
earth for a distance of one mile from the surface. 
One mile is taken as an approximate thickness since that 
seems to be a fair average of the thickess of sedimentary 
rocks over the surface of the earth. 
Assuming then that the earth is saturated with water to 
the depth of one mile, we have next to determine the relative 
amounts of its constituent rocks and their respective porosi- 
ties. 
The surface of the earth may be divided into two divisions, 
first, that covered with sedimentary rocks, and second, that 
*Loe. cit., p. 163, 
