514 THE DEPTHS OF THE SEA. [ciar. X. 
APPENDIX C. 
Notes on Specimens of the Bottom collected during the First 
Cruise of the ‘ Porcupine’ in 1869. By Davin Forsss, F.R.S. 
ATLANTIC Mvp contained in a small bottle marked ‘ Soundings, 
No. 20, 1,443 fathoms.’ 
A complete analysis of this sample shows its chemical com- 
position to be as follows :— 
Carbonate of lime . . vote be Seger aud 
Alumina! (‘soluble in ies , ite, ok tie Rear Rae eeluves 
Sesquioxide of iron (‘soluble in acids’) . . . 2°17 
Silica (in a soluble condition). . . a, Oe 
Fine insoluble gritty sand (rock débr a on ao Oma 
Waters 4 2) Ho rae Ge. ate a ee eee eee 
Organic matter . . . a oS 
Chloride of sodium and aie: soluble Sie Se! eee 
100°00 
If we compare the chemical composition as above with that 
of ordinary chalk, which consists all but entirely of carbonate 
of lime, and seldom contains more than from 2 to 4 per cent. 
of foreign matter (clay, silica, &c.), it will be seen that it differs 
chiefly in containing so very large an amount of rock-matter 
in a fine state of division. If we subtract the water, organic 
matter, and marine salts, which would probably in greatest 
part be removed before such mud could in process of ages be 
converted into solid rock, even then the amount of carbonate 
of lime or pure chalk would not be more than at highest some 
60 per cent. of the mass. 
As such deposits must naturally be expected to vary greatly 
in mechanical character and chemical composition, it would be 
' With phosphoric acid, 
