214 
THE VOYAGE OF H.M.S. CHALLENGER. 
word. Under a pressure of from 1000 to 3000 fathoms of superincumbent sea- water, 
carbonic acid assumes the form of a very dense liquid, which, far from issuing forth into 
the water above, must be presumed to be only gradually washed away by the currents, 
and in this manner distributed throughout the ocean. But be this as it may, it is reason- 
able to suppose that in the depths of the ocean there must be numerous bodies of richly 
carbonated water, and it is interesting to search in the Challenger records for evidence 
of their existence. The analyses of the numerous samples of sea- water air which were 
extracted by Mr. Buchanan in the course of the cruise, may be referred to here. These 
gases must contain all the free carbonic acid in addition to part of the loosely combined 
carbonic acid of the bicarbonate which was present in the original water. I have collected 
a few cases, in which both the volume of total gas extracted from a litre of water and 
the percentage of carbonic acid in the gas assumed high values ; and for the convenience 
of the reader transcribe them from my memoir: — 
No. of Water. 
D 8 
Carbonic Acid per 
1009 
2875 | 2850 
11 '6 c.c. 
1024 
2225 
11-5 „ 
771 
2325 
13-5 „ 
974 
3125 
14-3 „ 
1096 
2900 
15-8 „ 
I) stands for the deptli of the sea at which the sample named in Column I. was taken; 
8 for tie depth at which the .simple was collected. The last four entries refer to 
bottom waters. The carbonic acid is given in c.c. measured dry at 0° C. and 760 mms. 
pressure. These samples, as we see, all come from enormous depths, where the carbonic 
acid might most readily accumulate and assume an exceptionally high value ; and yet, 
own granting that the carbonic acid found in the boiled-out gas had all been in the 
water operated upon as free carbonic acid, its volume is less than 16 c.c. per litre, i.e., 
less than i J8o t ^ I = T} 3 ^ 1 °f that which the water might have taken up under 1 atmo- 
sphere’s pressure from an atmosphere of the pure gas. 
Pa-sing now to the samples of sea-water which were analysed for carbonic acid by 
Mr. Buchanan during the cruise, we meet with only two samples which contain a note- 
worthy quantity <-f five carbonic acid in addition to bicarbonate ; but even these could 
!«• designated, “carbonic acid wati i only by unduly stretching the definition of the term. 
< M.vioudy the Challenger staff in collecting their samples of sea-water never happened 
to strike on one of the carbonic ar id springs, except perhaps when the samples No. 383 
and 532 were collected ; it would have been remarkable if they had done so. 
I. ■ u- now proceed to a more detailed dcs, riplion of Mr. Buchanans carbonic acid 
determinations, as transcribed from his journal on pages 119 to 123 of the memoir. 
