THE DEPTH AND MARINE DEPOSITS OF THE PACIFIC OCEAN. 21 
so finely comminuted as to appear quite amorphous under the microscope. 
Phillipsite in minute crystals is also present, and this is not the least inter- 
esting point in the deposit. As regards the origin of this mud there is no 
evidence at hand to show exactly what it is, but according to the prelimi- 
nary report the sounding comes after a series of soundings which had revealed 
the presence of Coral Sand, in the vicinity of Manga Reva, in depths ranging 
from 225 to 1394 fathoms; this mud may thus possibly represent a very 
finely comminuted Coral Mud, the finer parts of which have been carried to 
the place where they were deposited, in a depth of 2225 fathoms. Refer- 
ence to the description will show that the calcareous constituents of this 
deposit are so minute that there is no mechanical objection to the supposition 
that they may have been held in suspension in the water and carried away a 
certain distance from their point of origin. It must be observed, however, 
that there is no known coral reef within 150 miles of this position. 
Volcanic Sand. A typical sample of this deposit was brought up from 
1552 fathoms, off Easter Island. 
Tue MINERAL CoNnsTITUENTS OBSERVED IN THE DirrERENT Deposits. 
The mineral constituents in the Globigerina Oozes found by the “ Alba- 
tross” are, as a rule, very small.'. When estimating the percentage of 
minerals, the plan adopted by the authors of the Challenger Report on 
Deep-Sea Deposits was adhered to; that is to say, particles that are not 
washed away together with the fine clay are put down as “ minerals.” 
These were weighed, and the percentage estimated after deducting the 
amount of siliceous organisms as indicated later. In two cases no mineral 
particles were observed ; in twenty-two cases the minerals were estimated 
as traces; in six cases the percentage is estimated at less than 1, and in the 
remaining six the percentage varies from | to 5. This fact is easily ac- 
counted for, as the ooze extends in a broad tract far from land, where the 
greater part of the mineral particles have a voleanic origin, continental 
débris being only accidentally met with. | 
Augite, plagioclase, volcanic glass, and magnetite are the minerals that usu- 
ally accompany Globigerina Ooze in this part of the Pacific; the oxides of 
iron and manganese, in the shape of minute grains, are seldom absent, and, 
even when not present as grains, it is to them that the brown color of the 
“fine washings” is due. 
1 Murray and Renard call particles exceeding 0.05 mm. in diameter “ minerals.” 
