980 
THE YOYAGrE OF H.M.S. CHALLENGER. 
Taking 45 mgrm. as a mean amount of carbonic acid, and 2000 fathoms (3660 
metres) as the mean depth of the ocean, this corresponds to a layer of carbon 3 '45 cm. 
thick over the area of the ocean. 1 It is right to observe here in connection with the 
determination of lime and of carbonic acid in sea water, that the freshly collected 
sample undoubtedly contains in almost all cases a certain amount of carbonate of 
lime suspended as living organisms, which, owing to their minuteness and transparency, 
flu not produce any apparent turbidity in the water. The distribution of these organisms 
is subject to local concentration, so that samples of water taken from neighbouring 
localities may, and usually do, contain very different amounts of this suspended matter. 
When these organisms consist, as regards mineral constituent, of carbonate of lime, this 
carbonate of lime will not be affected by the chloride of barium, but will be subject to the 
decomposing influence of the boiling solution of chloride of magnesium during the 
distillation of the sea water, and would account, at least in part, for the continued 
evolution of carbonic acid during the whole distillation, and for the want of uniformity in 
the results. Quantitative experiments made by Mr. Murray with the tow-net have 
shown that as much as 16 tons of carbonate of lime may be suspended in this form in a 
mass of sea water one mile square by 1 00 fathoms in depth. These organisms die, the 
1 In a lecture on his Challenger work delivered to the Glasgow Philosophical Society, Professor Dittmar sub- 
mitted a diagram showing the absolute composition of ocean salts. 
Unit=i billion tons = 10 12 x 1000 kilogrammes. 
Chloride of sodium, ..... 
35,990 'i 
Chloride of magnesium, .... 
5,034 1 From Prof. W. 
Sulphates, . . . . . 
. 2,192 1 Dittmar’s analyses 
Sulphate of zinc, ..... 
1,666 [> and oceanometric 
Sulphate of potash, ..... 
1,141 data given by 
Bromide of magnesium, . . . . 
100 | Boguslawski. 
Carbonate of lime, . . 
160 J 
46,283 
Total bromine (Dittmar), .... 
87-2 
Total iodine (Kobbstorffer), 
0-03 
Total chloride of rubidium (from C. Schmidt’s r 
Dialyses, as reported 
by Robb, Cliemisehe Geologie), ..... 26 '0 
Total mass of the ocean, .......= 1322355 units. 
Prof. Dittmar in the same lecture utilised certain data regarding the solids introduced into the ocean by rivers, 
which he found in Boguslawski’s Ozeanographie, for forming an estimate, however rough, of the rate at which these add 
to the amount of carbonate of lime. According to Boguslawski’s statement of the total water introduced by the thirteen 
principal rivers per annum on the one hand, and their average content of solids according to Bischoff on the other, it 
appears that these thirteen rivers contribute about L3375 x 10 9 tons of solids per annum, of which about one half may 
be said to be carbonate of lime. Assuming the carbonate of lime contributed by all rivers to amount to just so much, 
and comparing this with the 160 x 10 12 tons of the same substances which. are contained in the present ocean, it would 
take x^io 9 = 1 10400 years to bring up the total oceanic carbonate of lime to double its present amount; or 
1194 years to increase it by 1 per cent, of its present value. 
