REPORT ON THE COMPOSITION OF OCEAN-WATER. 
225 
temperature would vary in diurnal cycles, and even the calculated value of the volume 
of nitrogen per litre would be a periodic function of time, exhibiting its maximum at 
the hour corresponding to the minimum temperature and its minimum at the time of 
maximum temperature. The process of absorptiometric exchange, however, even at the 
constantly oscillating surface of the sea, is a thing of slow progress : it could not keep 
pace with the change of temperature, and the actual nitrogen curve would never go as 
high up or as low down as the theoretical one. In addition to this, the lower strata of the 
water will constantly add to or take away from the surface nitrogen by diffusion and 
occasional intermixture. All this holds for the oxygen likewise, except that the latter 
is liable to constant diminution by processes of oxidation. On the whole, however, we 
may assume that all the disturbing influences will only modify, but not efface, the course 
of events as prescribed by the law of gas- absorption. 
In regard to non-surface water, we have to confront a greater complexity of phenomena. 
The gas contents of a deep-sea water of course have nothing to do with the, in general low, 
temperature and high pressure prevailing at the respective place ; because the air was not 
taken up there but at the surface. Any given sample of deep-sea water must be 
presumed, in general, to be the result of the conflux of a number of surface-waters from 
a variety of places, but for the purpose of a preliminary survey, we may permit 
ourselves to view each sample of deep-sea water as having taken up its air at the 
surface at some one temperature t, and then sunk down unmixed. The volumes of 
nitrogen and oxygen per litre then should have the values assigned to them by the 
absorptiometric equations for this temperature. But while the ’ nitrogen (as long as 
that portion of water remains unmixed with other different water) remains constant, the 
oxygen will become less and less, through the processes of oxidation which in the deep go 
on without compensation. Hence, if there were absolute stagnation in the ocean anywhere, 
the proportion of dissolved oxygen there might be reduced ultimately to nothing. Amongst 
the many deep-sea waters' which were analysed for their gas contents, we found none that 
were quite free from absorbed oxygen, which confirms our conviction that absolute stagna- 
tion nowhere exists in the ocean, not even at its greatest depths. 
The actual relations can of course be ascertained only by observation and experiment. 
Mr. Buchanan, accordingly, in the course of the expedition, devoted a considerable 
portion of his time to the extraction of the gases from a great number of samples recently 
drawn from a variety of depths and geographical positions. He used for this purpose a 
method which had been worked out by Jacobsen, and employed by him successfully in 
the course of the German North Sea Expedition. The method is fully described on 
pages 141 and 142 of my memoir. It consists, essentially, in this, that the gas from 
a measured volume of the water is expelled by boiling, and driven into a previously 
evacuated glass tube, in which it is subsequently sealed up to be measured gasometrically 
and analysed in the laboratory. Of the many gas samples which Mr. Buchanan thus 
(PHYS. CHEM. CHALL. EXP. PART I. 1884.) A 29 
