EEPORT ON THE DEEP-SEA DEPOSITS. 
197 
The mean percentage of fine washings in the 70 samples of Red Clay is 85'35 ; the 
following table shows the relation between depth and percentage of fine washings : — 
18 samples from 2000 to 2500 fathoms, . 80’44 mean per cent, fine washings. 
42 „ 2500 „ 3000 „ . 85'80 
7 „ 3000 „ 3500 „ . 95-28 
3 „ over 3500 
. 80-281 
» >9 
The following table shows 
the average composition of 
the Challenger samples 
of Red Clay. It will be noticed that what we have called fine washings make up by far 
the larger part of the deposit, and it may be stated that the examination of many 
samples from other expeditions has yielded very similar results 
Pelagic Foraminifera, 
4-77 
Carbonate of Lime, . . - 
Bottom-living Foraminifera, 
0-59 
Other organisms. 
1-34 
— 6-70 
'Siliceous organisms, . 
2-39 
Residue, 
Minerals, . . . 
5-56 
Fine Washings, 
. 85-35 
93-30 
100-00 
Having thus pointed out the general results arising from 
a careful macroscopic and 
microscopic examination and analysis of a large number of Red Clays from many 
different regions of the ocean, it now remains to inquire how far these are confirmed and 
supported by chemical analysis. It seems rather unnecessary to dwell upon the difficulties 
connected with the interpretation of chemical analyses of mixed substances, of altered 
minerals, and of amorphous matters without any determinate composition like those 
which make up the greater part of Deep-Sea Deposits ; there cannot be a discussion of the 
analytical data in the same sense as if, for example, we had to do with an analysis of a 
crystalline rock. But when we take into account the data furnished by macroscopic and 
microscopic examination, we are able notwithstanding to draw some conclusions from the 
analyses of these deposits. 
The following table is compiled from the analyses made by the late Professor Brazier, 
as previously stated.^ The various deposits were submitted to the action of hydrochloric 
acid, and the portion dissolved in the acid was analysed separately ; the residue of this 
operation was afterwards treated with solvents, hence we divide the analytical tables 
into two divisions, the first containing the data relating to the part soluble in hydro- 
chloric acid, the second those referring to the insoluble portion. 
separate these matters by decantation ; hence arises in part the heterogeneity of these fine washings (see E. W. Hilgard, 
“ On the Flocculation of Particles,” &c., Anur. Journ. Sci., ser. iii. vol. xvii. p. 205, 1879 ; F. Senft, Die Thonsuhstanzen, 
p. 41, Berlin, 1879). 
^ See p. 193 about sample from 3875 fathoms. - Chap. i. p. 28; for details of analyses, see Apjiendix I. 
