504 REPORT OF COMMISSIONER OF FISH AND FISHERIES. — [2] 
36° and 37° F., even below 2,000 fathoms. But temperatures, practi- 
cally identical, have often been taken in about 1,000 fathoms, or even 
less. Therefore the minimum temperatures may be considered as practi 
cally reached at 1,000 fathoms, off our coast. Below that, there is very 
little change. Accordingly, many of the special deep-sea species range 
from 1,000 fathoms or less to below 2,000 fathoms, in this region. Serial 
temperatures were aiso taken at various localities. 
CHARACTER OF THE DEEP-SEA DEPOSITS. 
Some very interesting and important discoveries were made in regard 
to the nature of the materials composing the sea bottom under the Gulf 
Stream at great depths. These observations are of great interest from 
a geological point of view, as they illustrate the kinds of sedimentary 
rocks that may be formed far from land and in deep water, and some of 
them are contrary to the experience of other expeditions and not in ac- 
cordance with the generally accepted theories of the nature of the de- 
posits so far from land. The bottom between 600 and 2,000 fathoms, in 
other regions, has generally been found to consist mainly of “ globiger- 
ina 00ze,” or, as in some parts of the West Indian seas, of a mixture of 
globigerina and pteropod ooze. Off our northern coasts, however, al- 
though there is a more or less impure globigerina ooze, in such depths, at 
most localities beneath the Gulf Stream, this is by no means always the 
cease. The “ globigerina ooze” usually has the consistency of fine, 
sticky mud, commonly of a gray, dull olive-green or bluish color. When 
washed through a very fine sieve a variable, but often large, proportion 
remains on the sieve, composed chiefly of the shells of Globigerina and 
other foraminifera, of many kinds, but mostly minute species, which 
live at or near the surface of the sea and fall to the bottom when dead 
or disabled. With these are many larger forms, both of calcareous and 
sand-covered species, which live at the bottom. In many places there 
are large quantities of the brown, sandy, rod-like and triradiate species 
(Rhabdamminia), in which the rays become about half an inch long. 
These are mingled with small shells, annelid tubes, fragments of echi- 
noderms, otoliths of small fishes, &c., together with a variable propor. 
tion of true beach sand. The globigerina ooze, as found off our coast, 
even from below 1,000 fathoms, is always mixed with some fine siliceous 
and granitic sand, in which grains of quartz, feldspar, and mica can easily 
be distinguished under the microscope; in shallow water (100 to 400 
fathoms) the sand is coarser, with the grains easily visible to the naked 
eye, but of the same nature, and frequently contains much clay-mud. 
In several instances the bottom between 500 and 1,200 fathoms has been 
found to consist of tough and compact clay, so thoroughly hardened 
that large angular masses, sometimes weighing more than 50 pounds, 
have been brought up in the trawl, and have not been washed away 
appreciably, notwithstanding the rapidity with which they have been 
drawn up through about two miles of water. In fact, these masses of 
