KEPORT ON THE DEEP-SEA DEPOSITS. 
321 
(b) Rocks and Minerals derived directly from the Continental Masses. 
The widespread mineralogical products in marine deposits, derived from the ejections of 
submarine and subaerial volcanoes, have been dealt with in considerable detail in the pre- 
ceding section, and it is now necessary to consider the products of the second category, 
with a more restricted distribution, referred to at the beginning of this chapter, viz., those 
derived immediately from continental masses and emerged lands. In the first instance, 
we may direct our attention to the fragments of continental rocks, and their distribution 
in marine deposits, and afterwards consider the mineral particles derived from the dis- 
integration of continental rocks. 
Fragments of Continental Rocks. — It is unnecessary to treat in detail the fragments 
of rocks and minerals met with in the littoral and shallow- water zones. It is evident that 
these are, for the most part, derived from the adjoining coasts, by the action of tides, 
waves, currents, and winds upon the submerged and emerged rocks which crop out in the 
shaUow-water and littoral zones, or they have been transported from the far interior of 
the continents by the action of rivers and the ice with which rivers may sometimes be 
covered. In this work we have especially to deal with the deposits formed in the deep 
sea, that is beyond the 100-fathom line, or beyond what we have called the mud-line, 
where currents, waves, and other mechanical agents, play but an insignificant role. From 
d priori considerations we would not expect large fragments of the continental rocks to 
be carried seaward beyond the mud-line, except in what might be called abnormal condi- 
tions. The larger fragments met with in such abundance in the shallow-water and littoral 
zones are, by the mechanical and chemical actions of the region, continually subject to 
disintegration and decomposition; the minute products of their destruction are transported 
by currents into the stiller waters of the deep-sea region, where they slowly settle to the 
bottom, forming muds and oozes. The minute fragments thus transported seawards are 
rarely fragments of rocks, being principally made up of the more resistant crystalline 
particles, together with clayey and other amorphous matters. Indeed, under all 
normal conditions, it is rare to find fragments of rocks among the mineral constituents 
of a deposit, even in depths of a few hundred fathoms, and thirty or forty miles 
seaward, even although the shallow-water zone towards the land be of great extent, 
and covered with continental blocks of all dimensions and of varied lithological con- 
stitution. 
It is well known, however, that continental blocks are in exceptional circumstances 
carried to great distances fixed in the roots of trees, or entangled among the other 
materials that are borne as natural rafts into the ocean from great rivers. Eivers 
affected with ice during some part of the year are also the means of distributing 
(deep-sea deposits chall. exp. — 1891.) 41 
