124 NATURAL HISTORY MISCELLANY. 
Tue BOTTOM or THE SEA OFF THE Eastern UNITED STATES. — 
At the meeting of the Boston Society of Natural History, Nov. 
16, the President introduced Count L. F. de Pourtales, who spoke 
on the constitution of the bottom of the ocean off the east coast 
of the United States, south of Cape Hatteras, as developed by 
the soundings and dredgings of the United States Coast Survey. 
The chief constituent, he said, is silicious sand, from the coast 
line to about the one hundred fathom line, a limit which also coin- 
cides nearly with the inner edge of the gulf stream for a great por- 
tion of its course. Outside of this line the whitish, calcareous ‘*Glo- 
bigerina” mud prevails and extends probably under the greater 
part of the ocean. The silicious sand is replaced to the south- 
ward of the Vineyard Islands, and off the eastern end of Long 
Island, by a greenish or bluish mud, known by the navigators as 
the Block Island soundings. Similar mud is found off Sandy 
Hook in a range of depressions known as the mud-holes, which 
form a leading mark to find the port of New York in thick 
weather. In the neighborhood of New York a few rocky patches 
are found which require investigation. Near Cape Fear, also, 
rocky bottom is. sparingly found, affording a foothold to some 
corals, gorgonias and sponges. Otherwise the sand is pretty 
uniform in constitution, varying only in the size of the grain. 
A remarkable deposit of green-sand is found on the inner edge 
of the Gulf Stream, off the coast of Georgia and South Carolina. 
The bottom consists here chiefly of living and dead foraminifere, 
the chambers of the latter becoming filled with a silicate which 
injects even the finest ramifications of the canals of the shell. 
At first yellow, it gradually turns green, at the same time the shell 
proper decays and breaks off, leaving a cast, which by attrition 
and conglomeration with others often loses the characteristic form 
of a cast. Sometimes black pebbles are found, of which a sec- 
tion shows plainly the origin due to an agglomeration of casts of 
foraminiferz, ’ 
The dredgings made by the Coast Survey in the Straits of 
Florida have revealed the existence of a large bank, or deep sea 
platform off the Florida Reef, consisting of a highly fossiliferous 
limestone still in process of formation from the numerous shells, 
echinoderms and corals, mostly new to science, which live on it, at 
a depth of from one hundred to three hundred fathoms. Between 
this platform and the reef, the bottom consists of the detritus of 
