•236 
THE VOYAGE OF H.M.S. CHALLENGER 
deal of the percentage of alkalies must be referred to the presence of sea-salts retained in 
the deposits, as is shown by the following experiment. 
In speaking of the analyses of Red Clay and Globigerina Ooze, it was pointed out 
that, in their examination, the sea-salts that might be retained in the deposits should be 
taken into account. In order to arrive at an approximate notion on this point, the 
following determinations were made with a specimen of the Red Mud from Station 120, 
675 fathoms, of which we have just given the analysis. The substance was washed with 
warm and cold distilled water till the water no longer gave the reaction of chlorine. It 
was afterwards pulverised and treated with hydrofluoric and sulphuric acids. 1 ’4088 grms. 
of substance dried at 100° C. gave 0‘0496 grm. of chloride of sodium and potassium, and 
0T013 grm. of chloroplatinate of potassium, which corresponds to 0'0195 grm. of oxide 
of potassium and 0'0099 grm. of oxide of sodium — 
[No. 55.] Na.jO . . . .070 per cent. 
K 2 O .... 1-38 
In comparing this analysis with that given above, so far as regards the alkalies, it will 
be seen that there is about 1 per cent, more oxide of sodium in the unwashed than in 
the washed sample, which is doubtless due to the presence of chloride of sodium. 
The Red Muds probably occupy along the Brazilian coast about 100,000 square miles 
of the sea-bed. Similar red deposits are formed in the Yellow Sea off the Chinese coast 
near the mouth of the Yang-tse-kiang. 
Green Muds and Sands. 
In their composition, origin, and distribution these deposits resemble in many 
respects the Blue and Red Muds. Their chief characteristic is the presence in them of 
a greater or less abundance of glauconitic grains and glauconitic casts of the calcareous 
organism.s. There is also in these muds, mixed with glauconite, a greenish amorphous 
matter, which in part at least appears to be of an organic nature, for it blackens on being 
heated on platinum foil, lea\nng an ash coloured by oxide of iron. These muds and 
.sands are almost always develoi)ed along bold and exposed coasts, where no very large 
rivers pour their detrital matters into the sea. 
The collections of the “Tuscarora” indicate that in depths of 100 to 400 fathoms, ofi' 
the coast of California, there are l>lack sands which, if the specimens be in the state in which 
they were collected, are almost wholly composed of particles of dark green glauconite. 
The average <liametcr of the grains is about 0’6 mm., and mixed with them are a few 
Foraminifera and mineral j)articles of the same dimensions. It is rare, however, to find 
pure glauconitic sands like these, for the deposits contain, as a rule, many remains of 
cxilcareous organisms, mineral particles from the continental rocks, and a considerable 
