EEPORT ON THE DEEP-SEA DEPOSITS, 
177 
The deposits from depths greater than 1000 fathoms off the coast were Blue Muds 
containing from a mere trace to 4 per cent, of carbonate of lime, consisting to some 
extent of remains of pelagic organisms. In these deposits there were two layers — the 
upper red and the lower of a green or blue colour. Mineral fragments formed from 10 
to 30 per cent, of the whole; these were of a volcanic nature. From 1875 fathoms 
the trawl brought up several pumice stones and many large blocks having the same 
mineralogical composition and clastic elements as the mud itself ; these appeared to be 
indeed simply conglomerated portions of the bottom. Hardened conglomerations of 
deposit were also obtained from 420 fathoms. 
Japan to the Sandwich Islands . — The deposits between Japan and the Sandwich 
Islands (see Chart 36) were most interesting. The deposit in 1875 fathoms, off Japan, 
has already been noticed. In all the greater depths there was no carbonate of lime in the 
deposits, but it is instructive to notice that at two stations where the depth was less than 
the average, viz., 2300 and 2050 fathoms, there was respectively 17 and 56 per cent, of car- 
bonate of lime, consisting chiefly of the shells of pelagic Foraminifera ; this clearly shows, 
as has been already pointed out, that the amount of carbonate of lime deposited is in 
inverse relation to the depth, when as in this instance the surface conditions are the same 
or nearly so. It is to be noticed, however, that in 2225 fathoms close to the Sandwich 
Islands there was only a trace of carbonate of lime. A sounding (Station 247), where 
the depth was 2530 fathoms, was remarkable. In the upper part of the section brought 
up by the sounding tube there was a reddish clay without any carbonate of lime ; this 
layer was about an inch in thickness, and was somewhat sharply marked off from the lower 
layers, which were of a much lighter colour, and contained about 10 per cent, of carbonate 
of lime in the form of shells of pelagic Foraminifera. This condition of things might be 
explained by supposing that after the lower layers had been laid down, a subsidence of 
the bottom had taken place to the extent of 200 or 300 fathoms. All the deposits from 
the Japan coast to the 170th meridian of west longitude contained a very large number 
of the remains of surface-living siliceous organisms, chiefly Radiolaria. As the Sandwich 
Islands were approached, the siliceous organisms almost disappeared from the deposits, 
which were then almost wholly composed of the triturated fragments of pumice and 
amorphous clayey matter. For the relative depths and percentages of carbonate of lime, 
see Diagrams 17, 18, and 19. 
There were eleven trawlings and two dredgings during the trip, but on four occasions 
the line parted and the trawls with a considerable length of line were lost. The others 
were fairly successful and productive. On all occasions the bag of the trawl contained 
numerous pieces of pumice and many manganese nodules. Some of the rounded 
fragments of pumice were quite fresh and unaltered ; others had undergone profound 
alteration, and were frequently coated with successive layers of the peroxide of manganese. 
These pieces of pumice seem to have formed the centres of most of the manganese 
(deep-sea deposits chall. exp. — 1890.) 23 
