SUBMARINE DEPOSITS. 279 
near our coasts, was discovered by Bailey, from the examination of our 
bottom specimens. In some of them the whole process can be followed 
in the most interesting way. Thus we find, side by side, the tests per- 
feetly fresh, others still entire, but filled with a rusty-colored mass, 
which permeates the finest canals of the shells like an injection! In 
others, again, the shell is partly broken away, and the filling is turning 
greenish ; and finally we find the casts without trace of shell, sometimes 
perfectly reproducing the internal form of the chambers; sometimes, 
particularly in the larger ones, cracks of the surface or conglomeration 
with other grains obliterate all the characters. They even coalesce into 
pebbles, in which the casts can only be recognized after grinding and 
polishing. 
* Why this process of transformation should occur only in partic- 
ular localities is as yet unexplained. It is easy to distinguish this 
fresh formed greensand from the tertiary one off the coast of New 
Jersey, by the greater number of perfect tests of foraminifera mixed 
with it.” 
As was pointed out by Pourtalés, 16 is remarkable how closely 
the limits of the siliceous sand bottom coincide with the bound- 
aries of the cold current coming from the north, while the limits 
of the calcareous deposits correspond with the course of the 
warm waters of the Gulf Stream. We might almost trace its 
course by a study of the bottom specimens. On each side, as 
well as at the falls of the Gulf Stream south of Hatteras, ooze 
of varying composition was invariably brought up. The distri- 
bution of the foraminifera seems to throw considerable light on 
the circulation, and to give additional support to Commander 
Bartlett's view, based upon thermometrie sections, that the bulk 
of the Arctic current does not extend south of Hatteras along 
our coast, but that the colder and heavier waters of the northern 
current plunge beneath the Gulf Stream off Hatteras, and flow 
slowly on the outside edge of the Blake Plateau towards the 
equator. 
During the years 1875 and 1876, previous to my connection 
1 Many of the foraminifera dredged by due to foraminifera, but also in part to 
Pourtalés and myself in the Straits of other organisms, and he suggests that we 
Florida were filled with a yellow mass, may safely infer that this matrix has in- 
like that of the first stage of transforma- variably been formed in connection with 
tion into greensand. decaying organic matter. 
2 Bailey shows that the casts are not all 
