CHAPTER V. 
MINERAL SUBSTANCES OF TERRESTRIAL AND EXTRA-TERRESTRIAL ORIGIN 
IN DEEP-SEA DEPOSITS. 
The materials of organic origin in deep-sea deposits having been considered in the 
preceding chapter, we shall now turn our attention to the mineral particles, properly so 
called, which form a more or less considerable part of all marine deposits. 
When these mineral particles are regarded from the point of view of their origin, or 
rather of the source from which they have been immediately derived, they may be 
divided into three groups : — 
1. Mineral particles more immediately derived from the mechanical disintegration 
of the solid crust of the earth, and distributed by terrestrial forces over the 
bed of the sea. 
2. Mineral particles derived from extra-terrestrial regions, which play but an 
insignificant part in the mass of marine deposits, but are highly interesting 
from their origin, nature, and distribution. 
3. Mineral particles and substances formed in situ at the bottom of the ocean, as a 
result of chemical interaction with substances in solution in sea-water and 
materials of organic and inorganic origin undergoing deeomposition at the sea- 
bottom, which may therefore be called chemical products. 
These last (No. 3) will be dealt with in detail in Chapter VI., the present chapter 
being devoted to a consideration of the first two groups. 
I. Materials derived directly prom the Solid Crust of the Earth. 
If the materials derived directly from the solid crust of the earth, or from the under- 
lying layers, be looked at from a general point of view, they may be divided into two 
categories, corresponding in a certain way with the two great groups into which we 
have divided marine deposits, viz.. Pelagic Deposits and Terrigenous Deposits. The first 
of these categories comprises all those rocks and minerals projected in a fragmentary 
form from subaerial and submarine volcanoes during the present geological period. 
