118 
THE VOYAGE OF H.M.S. CHALLENGER. 
: mi. of carbonic ociil. The error in such a titration, according to my estimate, is 
rath t al-.vc ± 0“5 c.c., hence each of the numbers given for the actual carbonic acid 
I ■■ litn must be considered uncertain by at least rfc 1 mgrm. on that account alone. I 
f. ir w< must add another mgrm., and put down the limit of uncertainty in the carbonic 
per litre at ± 2 mgrms. Hence, practically, the evidence of the 13 analyses may be 
'Uinnud up by saying, that in all cases the “alkali” was substantially bicarbonate, un- 
iiit' d in any case with free carbonic acid, but very appreciably contaminated with 
normal carbonates in the 8 eases out of the 13 which are marked with asterisks in the 
! ist column. The numbera of course apply only to the samples as analysed; when 
ti' -■ <■» illceted they must be presumed, in general, to have been richer in carbonic acid. 
This would be more especially true of the five neutral samples. 
In conclusion, I append in a tabular form the results of the carbonic acid determinations 
in freshly drawn sea-water, which Mr. Buchanan made on board H.M.S. Challenger 
Table XII. 
> u n ig tlu proportion of total Carbonic Acid found in a selectionof Challenger Waters. 
Collected. 
Carbonic Acid inarms, per litre. 
Laboratory 
Number. 
Challenger No. 
Station. 
On 
At Depth oj 
fathoms. 
Calculated from 
Alkalinity. 
Found. 
1876. 
439 
1529 
March 9 
Bottom. 
331 
107-3 
105-6 
1875. 
379 
1134 
Sept. 8 
800 
272 
107-0 
106-1 
390 
1170 
Oct 4 
100 
280 
107-6 
98-7 * 
400 
1271 
„ 27 
0 
291 
105-7 
102-6 * 
406 
1313 
Nov. 9 
Bottom. 
296 
108-3 
101-0* 
414 
1397 
Dec. 30 
Bottom. 
303 
115-4 
111-6* 
1876. 
417 
1424 
Jun. 8 
0 
309 
91-4 
87-8* 
416 
1427 
„ « 
140 
309 
100-2 
101-5 
423 
1471 
Feb. 11 
0 
318 
103-8 
97-8 ) * 
423 
1471 
„ 11 
0 
318 
104-0 
99T / 
424 
/ 1471 l 
1 1473 / 
„ 11 
25 & 50 
318 
105-2 
98-1 ) 
424 
( 1472 1 
1 1473 / 
» 11 
25 & 50 
318 
105-2 
f 
102-2 ) 
421 
1 1463 1 
i 1464 / 
j 1463 1 
| 1464 ( 
„ 11 
50 & 100 
318 
106-9 
107-2 ) 
421 
„ 11 
50 Jc 100 
318 
107-2 
106-7 j 
f 1465 | 
tt 11 
200 k 400 
422 
i 1467 f 
318 
106-3 
106-4 | 
422 
f 1465 | 
( 1467 f 
» 11 
200 k 100 
318 
106-8 
107-0 j 
425 
1481 
14 
Bottom. 
320 
109 0 
t(?) 114-7 ) * 
425 
1481 
„ 14 
Bottom. 
320 
110-2 
103-2 j 
1481 
.Slink'-ii twice with 10 vol. air. 
100-6 
icrwt bottles. 
Tb» » c r>- niasln in the summer of 1881. 
t OUiofli l.lumhr. 
