BERKEY, GEOLOGY OF SOUTHERN MANHATTAN ISLAND 259 
In this tabulation only the three formations of recognized large impor¬ 
tance are taken into account, as follows: 
(1) The Fordham Gneiss, which is the lowest and oldest and most complex, 
including the Ravenswood granodiorite as a special variety; 
(2) The Inwood Limestone, or dolomite, which is the next younger and 
lies above the Fordham; 
(3) The Manhattan Schist, which is the uppermost formation. 
All types are referable to one or another of these three formations as 
varieties or facies or associated units of minor structural significance. 
Public Service Commission 
Borings made in Investigations for Subways 
There are six lines of borings across East River, as follows: 
a) 
b) 
c) 
d) 
e) 
f) 
South Ferry, N. Y.,to Joralemon St., Brooklyn. 
Old Slip, “ “ Montague “ 
Maiden Lane, “ “ Pineapple “ 
Beekman St., “ “ Cranberry “ 
Fourteenth St., “ “ No. Seventh “ 
Thirty-fourth St., “ “ Long Island City, R. R. Station. 
These materials are carefully labeled and housed in the rooms of the 
Commission. Samples of rock were taken by a diamond drill, and all are 
of small diameter. They have been examined especially for evidence as 
to the quality and variety of rock represented, and the classification and 
relationship to the standard local formations is indicated wherever possible. 
The datum to which all borings have been uniformly reduced is mean 
high water of the Rapid Transit Commission, which is 2.72 feet above mean 
sea level at Sandy Hook,— the datum of the U. S. Coast and Geodetic 
Survey, as well as that of the N. Y. City Board of Water Supply. 
