1S8 
THE VOYAGE OF H.M.S CHALLENGER. 
Tli.it these waters were relatively rich in oxygen, notwithstanding their high tempera- 
ture, is rather curious. 
This fact in the case of the first of our areas is easily accounted for by the low temperature 
prevailing there, which, of course, is unfavourable both to marine life and purely chemical 
• >xidati<ui. It is not so easily accounted for in the case of the second area, the less so, 
as the waters were collected there in summer-time (from November 1875 to March 1876). 
What puzzled me very much at first was the not unfrequent occurrence, in our table, of 
oxygen deficits. It is difficult to see how a sea-water can contain more oxygen 
p> r litre than is demanded by the law of gas-absorption. I tried to account for the 
apparent anomaly in a variety of ways, and at last was led to suspect that it may be the 
result of observational errors. Take, for instance, the first three entries in Table XV., 
that is, the three most striking cases. We have 
Water No., .... 
386 
1367 
387 
Station, ..... 
153 
301 
153 + 
Tcmjierature of water when collected (t Q ), 
. - 0°7 
15°-5 
+ 0°7 
Oxygen per litre found = a, 
8-26 
6-12 
7-27 
Oxygen „ calculated = b, . 
8-33 
578 
8-03 
Oxygen „ calculated from N 2 found = c, 
8-04 
5-92 
7-13 
(fc-a)- .... 
. +0-07 
-0-34 
+ 076 
(c-a)- .... 
. -0-22 
-0-20 
- 074 
We need only assume that the values for 
oxygen 
found, and those calculated from 
quantities of nitrogen found , are wrong, the one 
by + the other by 
TOTF °f If 8 
value, and c — a (i.e., the oxygen deficit as reported in the table) would be wrong by 
0-16 0 12 0T4 
Supposing these errors to have been committed, the residual oxygen deficits are not 
worth discussing. 
It is worth while to note, in passing, that the differences b—a, i.e., the excess of 
the oxygen calculated from the observed temperature t 0 , and the assumed (dry) pressure 
•• f 760 mm., over the oxygen found, in two out of our three cases, has a positive value. 
I><>. - the law of gan -absorption really hold for the ocean, in the circumstances prevail- 
ing at its surface ? I do not know whether it does or not. Imagine a mass of ocean- water 
in a state of incomplete saturation with air. It is in contact with a constantly renewed 
atmosphere, consisting always of very nearly 21 per cent, of oxygen and 79 per cent, of 
nitrogen gas. Will the successive instalments of oxygen^ and nitrogen q 2 be in the 
• \ -.i t. ratios of < 7 j = 0‘21 /?, to 7 2 = 0'79 ft 2 • It is not possible that at any stage short of 
absolutely complete SBturati n U.« enforced by repeated shaking with air, which is renewed 
°»>ly «ft«T it has come to a state of absorptiometric equilibrium with the water it is 
being s h aken with, say the oxygen, in virtue of a specifically strong affinity for sea-water, 
* ? up in a preponderating proportion? It was this consideration chiefly which 
caused me to re -discuss the results of the water-gas analyses on their own basis, inde- 
