30 
NATURE ; 
[May 8, 1873 
no 
been completely washed out of it on its way to the sur- 
face. The bottom water gavea specific gravity of 1°02504 
at 19°6 C., that of the surface being 102617 at 21°3 C. 
While sounding, the current-drag was tried, and indicated 
a slight north-westerly current. : 
As the attempt to dredge on the previous day had been 
unsuccessful, it was determined to repeat the operation 
with every possible precaution on the 26th. The morning 
was bright and clear, and the swell, which had been 
rather heavy the day before, had gone down considerably. 
A sounding was taken about 10 o’clock A.M. with the 
“Hydra” machine and 4cwt. The sounding was tho- 
roughly satisfactory, a sudden change of rate in the 
running out of the line indicating in the most marked 
way when the weight had reached the bottom. During 
the sounding a current-drag was put down to the depth 
of 200 fathoms, and it was then ascertained that, by 
means of management and by meeting the current by an 
occasional turn of the screw, the ship scarcely moved from 
depth, totally different from what we had been in the 
habit of meeting with in the depths of the Atlantic. For 
a few soundings part of the ooze had been assuming a 
darker tint,and showed on analysis a continually lessening 
amount of calcareous matter, and, under the microscope, 
a smaller number of foraminifera. Now calcareous 
shells of foraminifera were entirely wanting, and the only 
organisms which could be detected after washing over 
and sifting the whole of the mud with the greatest care, 
were three or four foraminifera of the Cristellarian series, 
with their tests made up of particles of the same red mud. 
The shells and spines of surface animals were entirely 
wanting ; and this is the more remarkable as the clay- 
mud was excessively fine, remaining for days suspended 
in the water, looking in colour and consistence exactly 
like chocolate, indicating therefore an almost total absence 
of movement in the water where it is being deposited. 
When at length it settles, it forms a perfectly smooth red- 
brown paste, without the least feeling of grittiness between 
the fingers, as if it had been levigated with extreme care 
her position during the whole time the lead was running 
out. The depth was 3,150 fathoms ; the bottom a per- 
fectly smooth red clay, containing scarcely a trace of 
organic matter—merely a few coccoliths, and one or two 
minute granular masses. The thermometer indicated a 
bottom temperature of 1°'9 C. ; 
The small dredge was sent down at 2.15 P.M. with two — 
hempen tangles ; and, inorder to efisure its reaching the 
bottom, attached to the iron bar below the dredge which 
is used for suspending the tangles, a “ Hydra” instrument 
with detaching weight of 3cwt. Two additional weights 
of 1 cwt. each were fixed to the rope 200 fathoms before 
the dredge. 3,600 fathoms of rope were payed out—1,000 
fathoms 2 in. in circumference, and the remainder (2,600 
fathoms) 2}in. The dredge came up at 10.15 P.M. with 
about 1 cwt. of red clay. 
This haul interested us greatly. It was the deepest by 
several hundred fathoms which had ever been taken, and, 
at all events coincidentally with this great increase in 
Base 
Fic. 1.—Potyorocon_Amapou Wy. T. 
for a process in some refined art. 
almost pure clay, a silicate of alumina and the sesqui- 
oxide of iron, with a small quantity of manganese, 
It is of course a_ most interesting question whether the 
peculiar nature of this deposit is connected in any way 
On analysis it is 
with the extreme depth. I am certainly inclined at 
present to believe that itis not. The depth at Station 5 
was 2,740 fathoms, and on that occasion foraminifera 
were abundant, and several bivalve mollusca were taken 
living. I cannot believe there can be any difference 
between a depth of 2,740 fathoms and one of 3,150 so 
essential as to arrest the life of the organisms to the 
secretions of whose tests the grey Atlantic ooze is due. 
I am rather inclined in the meantime to attribute this 
peculiar deposit to the movement of water from some 
special locality—very possibly the mouths of the great 
South American rivers—the movement possibly directed 
in some measure by the form of the bottom. This, how- 
ever, is a question for the solution of which we may hope 
to procure sufficient data. WYVILLE THOMSON 
