662 
Proceedings of the Eoycd Society 
nor swabs were used. In the tow-net there was a little of the deposit 
evidently knocked up by the action of the trawl in passing over the 
bottom, and in the trawl were many animals. 
2nd haul. — Dredge with two swabs attached was put over at 
8 p.m. on the 11th, and hauled in at 4 a.m. on the 12tli August. The 
bag of the dredge was full of a grey mud (about 40 litres) with 
Echinoderms, Annelids, Gasteropods, &c. 
Description of the Deposit .* 
Grey mud coherent, finely granular, homogeneous, earthy, 
calcareous, has a greenish tinge when wet. 
* The description of these deposits has been made upon the plan which we 
have adopted in our work in preparation upon the oceanic deposits, to form 
one of the reports on the scientific results of the “Challenger” expedition. 
This is not the place to develop the reasons which have guided us in adopt- 
ing this mode of description, or to expose, in detail, the methods which we 
have systematically employed for all the sediments which we are engaged in 
describing. These will be given in great detail in the introduction to our 
“ Challenger” report. We limit ourselves here, in order to facilitate the com- 
prehension of our descriptions, to describe the order of our tables, and to 
explain the meanings and arrangement of terms and abbreviations. 
The description commences by indicating the kind of deposit (red clay, grey 
mud, globigerina ooze,&c.), and comprises the microscopic determination of 
the characters of the deposit, when wet or dry. 
When we have not given a complete analysis of the deposit, we have always 
determined the amount of Carbonate of Calcium. This determination was 
generally made in estimating the carbonic acid. We took usually, for this 
purpose, a gram of the substance, and calculated in this manner the carbonate 
of calcium. Weak and cold hydrochloric acid was used. However, as, inde- 
pendent of the carbonate of calcium, the deposits often contain carbonates of 
magnesia and iron, the results calculated in placing the carbonic acid to CaO 
are not perfectly exact. These carbonates of magnesia and iron are almost 
always in very small proportion, and the result of the process gives that degree 
of accuracy which we think necessary. The number which follows the words 
“ carbonate of calcium ” indicates the percentage of CaC0 3 ; we then give the 
general designations of the principal calcareous organisms forming the carbonate 
of lime in the deposit. The part insoluble in the acid, after the determination 
of the carbonic acid, is designated in our descriptions by the name Residue. 
The number which follows this word indicates its percentage in the deposits ; 
then follow the colour and principal physical properties. This residue is 
washed and submitted to regular decantations, which permit the several 
elements of this insoluble portion being separated according to their density. 
We divide these portions into three groups — (1) Minerals, (2) Siliceous Organ- 
isms, (3) Fine Washings. 
1. Minerals . — The number within brackets indicates the percentage of par- 
ticular minerals and fragments of rocks. This number is the result of an 
