504 Proceedings of the Royal Society 
the chemical action of sea water. We will return to these influences 
presently when describing the distribution of the various kinds of 
dej^osits and their reciprocal relations, especially in those regions of 
the deep sea far removed from the mechanical action of rivers, 
waves, and superficial currents. The action of life as a geological 
agent has been indicated under the heading Materials. 
Methods . — We give here an example showing the order followed 
in describing the deposits examined. 
Station 338; lat. 21° 15' S., long. 14° 2' W.; 21st March 1876; 
surface temperature 76° ‘5, bottom temperature 36° ’5, depth 1990 fathoms. 
Globigerina Ooze, white with slight rosy tinge when wet ; granular, 
homogeneous, and very slightly coherent when dry ; resembles chalk. 
i. Carbonate of Calcium, 90 ‘38 per cent., consists of pelagic Foraminifera 
(80 per cent.) ; coccoliths and rhabdoliths (9 per cent.) ; Miliolas, Dis- 
corbinas, and other Foraminifera, Ostracode valves, fragments of Echini 
spines, and one or two small fragments of Pteropods (1‘38 per cent.). 
ii. Residue, 9'62 per cent., reddish-brown ; consists of 
1. Mmerals [F62] m. cli. 0*45 mm., fragments of felspar, hornblende, 
magnetite, magnetic s];therules,a few small grains of manganese, and pumice. 
2. Siliceous Organisms [I'OO], Kadiolarians, spicules of Sponges, and 
imperfect casts of Foraminifera. 
3. Fine TFashings [7’00], Argillaceous matter with small mineral 
particles and fragments of pumice and siliceous organisms. 
The description of the deposits has been made upon this plan 
which was adopted after many trials and much consideration. 
This is not the place to give the reasons which have guided us 
in adopting this mode of description, or to give in detail the methods 
that we have systematically employed for all the sediments which 
we are engaged in describing. These will be fully given in the intro- 
duction to our “ Challenger” Keport. We limit ourselves here to 
explaining the meanings and arrangement of terms and abbreviations, 
so that the method may be understood and made available for others. 
The description commences by indicating the kind of deposit (red 
clay, blue mud, globigerina ooze, &c.), with the microscopic charac- 
ters of the deposit, when wet or dry. 
We have always endeavoured to give a complete chemical analysis 
of the deposit, but when it was impossible to do this we have 
always determined the amount of Carbonate of Ccdcium. This 
determination was generally made by estimating the carbonic acid. 
