140 
THE VOYAGE OF H.M.S. CHALLENGER. 
\v].'T< th' symbols /?,, /3 : , stand for the coefficients of absorption considered with refer- 
.‘ii. t-i one litre of sea-water, the gas being assumed to be measured in cubic centimetres 
r. dm .'d to 0 C., and the dry-gas pressure P = 7G0±.r at which the absorption takes place. 
lint this theoretical relation could not be supposed to be realised in nature, even if 
organic matter were entirely absent. Because there are currents of water constantly 
flowing forwards and backwards, and preventing the attainment anywhere of an absolutely 
• ■ ‘list mt temperature; and even supposing an area of the surface stratum to be stagnant 
and at a constant temperature, the current of ocean-water containing gas of different 
omposition Mowing past underneath, would, by diffusion, constantly either add to or 
<1 ti i t from the theoretically calculated proportion of any of the three gases, according 
to laws as yet unformulated. But the most potent of actual causes of disturbance 
are the continual processes of life and of decay in the ocean, which constantly tend 
' diminish the quantity of oxygen, and (on the whole) to add to the quantity of carbonic 
acid present The quantity of the nitrogen must be presumed to be at least relatively 
indi jM n»h nt of these influences, and, at any place and any depth, to be approximately equal 
t" that which that portion of water took up, according to the laws of gas-absorption, when 
it was in contact with the atmosphere. It does not follow in any given case that this 
quantity can be calculated from any procurable data, because in general any portion of 
internal ocean water must be presumed to be a mixture of surface waters from a 
multiplicity of sources. Supposing that the quantity of nitrogen corresponds to 
complete saturation by air at the surface, at one certain temperature, t, then the 
oxyg.-n associated with the nitrogen will in general be less than that calculated 
fn»m this amount of nitrogen and the temperature, while no calculation will give us, 
even approximately, the amount of carbonic acid. 
Strictly speaking, the same remark, within rather wide limits, holds good for the 
oxyg* n and the nitrogen; but since the ocean, during the thousands of years of its 
• \;'t<-nce, must be supposed in every respect to have arrived at a state of approximate 
dyn rnic equilibrium, it should be possible, on the basis of a large number of exact 
■ j" rimental determinations, to represent the proportions of the three atmospheric gases 
p; '<-111 in a given sample a.s functions of the latitude, longitude, depth, and time at which 
■amph- wa- taken. At this most important problem of physical oceanography a number 
of chemists have consciously or unconsciously been working; but there is no need here to 
twee the history of this subject back any further than the year 1872, when Jacobsen, 
capacity a- chemist to the German North-Sea Expedition, investigated the 
q • « f ib -.rbed nitrogen and oxygen in a most masterly manner, and, for the first 
n • i at really reliable n suit . What his predecessors had done is not worth 
’ ■ or-c tli.'ir methods of working fell far short of the necessary degree of 
' ' , • 1 ■ ob-cn, instead of endeavouring, as some of them had done, to determine the 
* Annalen <1. Chemie (for 1873), Bd. clxvii., p. 1 et neq. 
