MAGNETITE IRON DEPOSITS OF SOUTHEASTERN NEW YORK 27 
structural breaks in the Precambrian rocks of the Highlands °° and 
to detect the presence of infaulted blocks of Cambro-Ordovician 
sediments in the crystallines of the Precambrian. By an agreement 
effected between the Board of Water Supply of the city of New York 
and Dr John M. Clarke, the state geologist, the geologic data 
acquired in the preliminary and final surveys for the aqueduct were 
intrusted to Doctor Berkey for summation,® the data appearing in 
a bulletin of the State Museum. Not only is this bulletin a scientific 
record of very accurate observations, but also an illustration of the 
application of geology to engineering problems and a manual of 
great educational value. The unusual difficulties encountered in 
making the exploratory borings preparatory to constructing the 
pressure tunnel under the Hudson river from Storm King mountain 
on the west bank of the river to Breakneck mountain on the east 
are excellently described by Kemp*? who was associated with 
Doctor Berkey in the geological work on the aqueduct. The 
peculiar rock conditions found when the tunnel was finally con- 
structed (“popping rock,” p. 5) are described, as well as other 
features of much interest. 
In a paper presented to the Eleventh International Geological 
Congress in 1910, Professor Kemp “ discussed the correlation of the 
belts of crystalline limestone and schist extending from New York 
City to the Highlands, a distance of over 40 miles, with the Hudson 
River slates and the Wappinger limestone, regarded by Mather, 
Dana, and Merrill as the unmetamorphosed equivalents of the south- 
ern crystallines. Kemp remarks: 
There is indeed a striking parallelism between the two. Thus on the south 
of the Highlands, which form a ridge of the oldest rocks of this section 
and which cross the river from northeast to southwest, we find a very heavy 
development of mica-schist, resting conformably on a thick stratum of dolo- 
66 Berkey, C. P. Structural and Stratigraphic Features of Basal Gneisses 
of the Highlands. N. Y. State Mus. Bul. 107, 1907; idem, Prominent Struc- 
ture of the Northern Margin of the Highlands; Abstract, Annals N. Y. 
AMEBL, SS Ais AiO,  iu@uz, 
67 Berkey, C. P. Geology of the New York City (Catskill) Aqueduct. 
N. Y. State Mus. Bul. 146. 1011. 
68 The problems of special interest involving structural and other condi- 
tions in various localities in the Highlands are: Pagenstechers gorge and 
Storm King mountain, ch. VIII; Hudson River Crossing, ch. II-III; rock 
conditions at Foundry Brook, ch. IX; geology of Sprout Brook, ch. X; and 
Peekskill Creek valley, ch. XI. 
69 Kemp, J. F. The Storm King Crossing of the Hudson River by the 
New Catskill Aqueduct of New York City. Amer. Jour. Sci. (4), v. 34: 1-11. 
1912. 
70 Kemp, J. F. Precambrian Formations in the State of New York: Con- 
gres Géologique Internationale, Comptes Rendus 11, 1910, p. 699-719. Stock- 
holm, 1912. 
