on the Approaches to New York Bay. 479 
logical formation having a vertical range of nearly six thou- 
sand feet. The sea-bottom within this area may contain the 
outcroppings of strata of various composition and of different 
ages, but these strata must be assumed to be always more or 
less argillaceous. The shoaler soundings generally show a 
strong admixture of sand while the deeper ones appear as purer 
clays. At about the depth of 1000 fathoms the clay gives 
way to the globigerina ooze; but in some instances clay has 
been found by the Fish Commission at depths over 1500 
fathoms. In view of the fact that in coast regions the distri- 
bution of “sand” and ‘‘mud” bottoms is very often the result 
of ocean currents, it appears proper to define the extent to 
which such currents may have affected the limits of our “clay 
region,” 
being bare of drift, we can safely 
nd FE indicate the Ngan seat 
of glacial drift on this part of the continent. e thickness 
of the cover of diluvial ‘drift in He Sy submerged 
vall to be at the utmost about sixty feet. 
“The a River Fiord.—The deep ravine mentioned above 
as one of the remarkable features of the sea-approaches to 
