SUMMARY OF RESULTS. 
1461 
a very heterogeneous arrangement of the superficial portions of the earth’s crust. 
In some regions sandstones and highly siliceous rocks prevail, in others limestones 
and clays with much iron and manganese. During the Challenger Expedition, particles 
of quartz Avere found to be almost wholly absent from the deposits towards the central 
portions of the ocean basins, but small quartz particles were found abundantly in 
all the terrigenous deposits laid down near the shore. As continental rocks are largely Terrigenous 
made up of free quartz particles, and all contain particles of quartz, it follows that they 
must have been formed from the deposits laid down near to pre-existing land. Eocks, 
made up in this way of terrigenous deposits, appear to have been again and again 
pushed up to form new land in the gradual evolution of the surface features of the 
planet, and to have been again and again torn down by atmospheric agencies, 
the various strata becoming more simple in composition, while the land masses, on the 
whole, have become more complex in structure at each revolution. Among the strata 
of the continents there are numerous examples of rocks which were apparently 
laid down in a deep sea, but a deep sea which must have been in more or 
less close proximity to some then-existing continental land. It is, on the other 
hand, extremely doubtful whether any continental rock has been laid down 
under physical conditions similar to those under which pelagic deposits are now being 
formed on the sea-bed beyond 300 miles from continental land. A broad distinction 
is to be drawn between 'pelagic and terrigenous deep-sea deposits. Quartz particles 
are almost wholly absent from the former, while they may make up 80 per cent, of 
the latter. 
In the central parts of the Pacific and Indian Oceans there are in Amry deep water Pelagic Deposits. 
dark chocolate coloured deposits containing large quantities of iron and manganese, 
together with immense numbers of zeolitic crystals, small black spherules with metallic 
nuclei and other spherules of cosmic origin, great numbers of sharks’ teeth and bones of 
whales, some of these latter belonging to extinct species. All these objects may be 
present as the nuclei of large manganese-iron nodules. At first I was inclined to regard 
the peculiarities of these deposits as being in some way due to hypogene action, but all 
these peculiarities may be better explained b}^ regarding them as the results brought 
about by chemical changes on areas of the sea-bed where there has been an extremely 
slow rate of accumulation, and where all the materials of the deposit have for a long 
time been exposed to the action of sea-Avater. We now knoAv that manganese can by 
successive deoxidations and reoxidations in, and at the surface of, marine deposits be 
transported on the floor of the ocean from coast regions to the central and deeper 
areas of the Ocean Basins.^ Lime, iron, manganese, magnesia, and the alkalies seem 
to have accumulated in the ocean and in the abysmal deposits at the expense of 
1 Murray and Irvine, On Manganese O.vides and Manganese Nodules in Marine Deposits, Trans. Roy. Soc. Edhi., 
vol. xjxvii., p. 740, 1894. 
(summary of results chall. exp. — 1894.) 
184 
