20 THE DEPTH AND MARINE DEPOSITS OF THE PACIFIC OCEAN. 
percentage of calcium carbonate varies from 0 to 20, 0 per cent occurring 
nine times, and the mean being 5.33 per cent. The mean percentage of 
calcium carbonate in the Red Clays of the whole ocean is, according to the 
“Challenger” researches: 8.39 per cent in 18 samples from 2000 to 2500 
fathoms, 7.16 per cent in 42 samples from 2500 to 3000 fathoms. The 
depths are of the same order of magnitude, and yet the percentage for 
the whole ocean is strikingly higher. The lower percentage in the case 
of the “ Albatross” Red Clay may very possibly be connected with the distri- 
bution of the surface currents in this part of the ocean, and has certainly 
nothing to do with depth, as many of the samples of Globigerina Ooze were 
collected in depths not much less than those in which the Red Clay was 
found, the average depth for Globigerina Ooze being 2001 fathoms against 
2404 fathoms for Red Clay, and in a few cases Red Clay was found in 
depths which at other stations allow Globigerina Ooze to be deposited. As 
an illustration we may mention the Red Clay of Station 4544 (lat. 10° 38’ N., 
long. 106° 47’ W.), where, although the depth is only 1955 fathoms, the 
amount of calcium carbonate is equal to 0 per cent. 
Diatom Ooze is represented by a most interesting sample which will be 
found fully described later, and Radiolarian Ooze is represented by two un- 
labelled samples; Pteropod Ooze is not represented in the collection. 
Terrigenous Deposits. Green Mud was found by the “‘ Albatross” in two 
localities, in 776 and 1036 fathoms, and Green Sand in 556 fathoms. The 
calcium carbonate in one Green Mud was as high as 25 per cent; in the 
other only traces were found, while the percentage in the Green Sand was 5. 
Glauconite is, of course, the characteristic mineral in these deposits, and 
is usually accompanied by a green flocculent matter, to which Sir John 
Murray and the late Professor Renard rightly attributed a vegetable origin. 
To test the question two samples from the Agulhas Bank were placed in 
small bottles and left to digest, the one in ether, the other in chloroform, 
and in both cases the solvent took a pronounced green tinge, a fact which 
strongly supports the above-mentioned view. 
Blue Mud was found off Callao in 1490 and 1949 fathoms; in the former 
there was no calcium carbonate, while the latter contained 5 per cent. 
Calcareous Mud. This name is applied here to a rather peculiar deposit 
met with in lat. 21° 4’ &., long. 133° 1’ W., in 2225 fathoms. The re- 
markable fact about this mud is that it is essentially composed of coccoliths 
and Tunicate spicules, together with a large quantity of calcium carbonate 
