THE DEPTH AND MARINE DEPOSITS OF THE PACIFIC OCEAN. 163 i 
under ordinary circumstances expect to find a Globigerina Ooze. Indeed, in ! 
the case of Station 4719, the adjacent stations, where the depth is quite / 
similar, give Globigerina Oozes containing over 50 per cent of calcium car- | 
bonate. It seems, therefore, that in these exceptional cases some hypogene 
action has taken place, resulting in the removal of the whole of the calcium 
carbonate shells and remains from the deposit. That some such action had 
taken place at the bottom of the sea wasindicated ata few stations during the 
“Challenger” expedition, but from the larger number of instances revealed 
by the examination of Dr. Agassiz’s collections this explanation seems now 
clearly necessary. Again, at Station 4531, where the percentage of calcium 
carbonate is 72, the calcareous shells have disappeared, and the deposit con- 
sists of a large quantity of comminuted particles of calcium carbonate together 
with coccoliths and Tunicate spicules. Probably this calcium carbonate has 
all been derived from the shells of marine organisms, but these have disap- 
peared through some hypogene action. Possibly there may also have been a 
chemical precipitation of calcium carbonate. 
The mineral particles found in Red Clay and Globigerina Ooze are nearly 
always of volcanic origin, and we may once more draw attention to the great 
role that palagonite and allied minerals play in the southern Pacific Ocean. 
This distribution of decomposed basic volcanic elements coincides with the 
frequent occurrence of phillipsite, and explains the presence of this mineral 
in Globigerina Ooze as well as in Red Clay, its origin being thus independent 
of a question of great depth. The same may be said of manganese concre- 
tions and nodules; being generally found far from land, the origin of the 
manganese is not to be sought for in the products of continental erosion, but 
in those of the decomposition of the volcanic elements we have found to be 
so widely distributed. 
It must be remembered that the Red Clay of the deeper parts of the ocean 
has no definite composition. It is made up of materials from very different 
sources, as we have just seen. In the South Pacific basic volcanic rocks, like 
sideromelan and palagonite, predominate ; in the North Pacific the triturated 
fragments of pumice are most abundant. In some parts of the Atlantic the 
Red Clay receives additions which have a continental origin, as in the case 
of sand grains transported by the Harmattan Winds off the west coast of 
Africa. 
Dr. W. A. Caspari, who has been assisting in chemical examination of the 
deposits in the “Challenger” Office, has prepared some notes upon his exami- 
