504 REPORT OF COMMISSIONER OF PISH AND FISHERIES. [2] 



36© and 57° F., even below 2,000 fathoms. But temperatures, praoti 

 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 also 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 mainlj'^ of " globiger- 

 ina ooze," or, as in some parts of the West Indian seas, of a mixture of 

 globigerina and pteropod ooze. Oft' 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 

 case. 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 miuute 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 Hot 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 



