SUBMARINE DEPOSITS. 263 
The various kinds of deep-sea deposits are named after the 
fragments or organisms predominating in each, or so numerous 
as to be characteristic. 
The deposits found in more or less close proximity to conti- 
nental shores are chiefly made up of the débris brought down 
by rivers or torn away from the adjoining coasts. These are 
Fig. 178. — Black Spherule with metallic Fig. 179. — Spherule covered with a coating 
nucleus. 20. (Chall.) 3,150 fathoms, of black shining magnetite. The most 
Atlantic. External coating removed to common shape showing the depression 
show the metallic nucleus. (Chall.) found at the surface. 20. 2,375 fath- 
oms, Pacifie. (Chall.) 
called generally terrigenous deposits, and consist of quartz sands, 
marls, blue, red, and green muds, and greensands. Around the 
shores of voleanie islands and coral islands, the deposits are vol- 
canic muds and sands, and coral muds and sands. 
Masses of rock, or huge boulders, but little altered, are found 
close inshore, near the spot from which they originated. Far- 
ther out, these are replaced by coarse shingle and gravel, 
merging gradually, in the progress seaward, into the finer mate- 
rial on the bottom. 
The fragments of quartz, feldspars, mica, together with frag- 
ments of gneiss, granite, mica schist, and other ancient and 
stratified rocks, which are very abundant in the deposits along 
continental coasts, become gradually smaller in size and fewer 
in number as we proceed towards the deeper and more distant 
parts of the oceanic basins, when they become no longer re- 
cognizable in the deposits, but form an impalpable ooze ; the 
case, however, is different with those regions of the ocean which 
are affected by floating ice and icebergs, and certain other 
1 Along our coasts, icebergs loaded northern regions drift south as far as lati- 
with boulders and detritus brought from tude 36°, and distribute foreign material 
