EEPOET ON THE DEEP-SEA DEPOSITS. 
171 
agglutinated or coagulated by an argillo-calcareous cement which is not in great 
abundance. Some of the shells are entirely filled with pale green glauconite, others 
only partially. The intervals between the shells are not filled up with the cementing 
matter, and these concretions appeared to be the last phase of disintegration. 
Those of the second variety are very irregular in shape, and consist of large pieces of 
a hard rock traversed in all directions by large and small perforations, with a diameter 
var 5 ung from 1 to 4 centimetres. These blocks have thus a cavernous or coarse cellular 
appearance. The perforations are covered, like the surface of the rock, with organisms, as 
Sponges, Polyzoa, &c., and rough to the touch. The smaller perforations have sometimes 
the appearance of having been produced by lithophagous Molluscs. These concretions 
have the hardness of calcite ; the fragments freshly broken are white-grey. A microscopic 
examination shows that they are mainly composed of various species of pelagic Foramini- 
fera. Treated with dilute acid the concretions decompose with effervescence, leaving a 
residue of 20 ’44 per cent., essentially composed of amorphous matter and glauconitic 
casts of the Foraminifera, these last being brown or green and feebly transparent. The 
greenish casts present most of the characters of true glauconite. In the residue there 
are also a few grains of felspar and quartz. A section of these concretions resembles in 
most respects a section of a hardened Globigerina Ooze from tropical regions, and near 
a continental shore (see PI. XII. fig. 2). In this case, hov/ever, the shells are nearly 
all filled and cemented by the finely granular carbonate of lime, while in a Globigerina 
Ooze they are empty. It is not improbable that these large concretions or rock-frag- 
ments are hardened portions of a deep-sea deposit formed at a much greater depth, and 
subsequently elevated into the position in which they were found, probably by the same 
elevation as that which upheaved the neighbouring islands. 
The deposit at 2800 fathoms was a fine-grained Volcanic Mud containing only a trace 
of carbonate of lime in the form of a few Pulvinulina shells. Mineral particles of 
volcanic origin made up about 60 per cent.; these were angular fragments of felspars, 
volcanic glass, augite, magnetite, and andesitic lapilli, having a mean diameter of 
0'2 mm. There was also 5 per cent, of Sponge spicules, Radiolaria, and Diatoms. At 
200 and 360 fathoms close to Banda (see Chart 33) the deposits consisted essentially of 
volcanic materials with a few pelagic Foraminifera. The dredge brought up several frag- 
ments of volcanic rocks and 23umice measuring from 2 to 1 0 centimetres in diameter. Corals, 
siliceous Sponges, and calcareous Algae. 
In 17 fathoms off Banda the bottom was a sand or gravel with 52 per cent, of 
carbonate of lime made up of Foraminifera, Gasteropod, and Lamellibranch shells, 
Echinoderm fragments. Corals, and calcareous Algae, 
Banda to Amboina . — The deposit in 1425 fathoms (see Chart 31) was a Blue Mud 
containing 31 per cent, of carbonate of lime. The surface layer, about half an inch in 
thickness, was brownish in colour, while the deeper ones were blue and very compact. 
