REPORT ON THE COMPOSITION OE OCEAN-WATER. 
213 
and assuming the ocean at a given time everywhere contained its surplus base as 
sesqui-carbonate, then the water of the tropics would constantly give out carbonic 
acid to the atmosphere and tend to raise its 0-0003 atmosphere of carbonic acid 
pressure to the dissociation tension corresponding to the temperature. Passing now 
from the equator, either way, to colder and colder latitudes, this carbonic acid emis- 
sion becomes less and less intense, until, in a certain belt of temperature which 
prescribes to the dissociation tension the value 0‘0003, this emission becomes nil, 
and proceeding towards the pole to colder and colder latitudes, the water will take in 
carbonic acid at a greater and greater rate, and tend to convert its surplus base into fully 
saturated bicarbonate, which stage of saturation is the more likely to be reached the 
nearer we come to either pole. The number of equivalents of carbonic acid present for 
every one equivalent of surplus base would, in fact, be a function of the temperature of 
the water, or approximately of the latitude. But the actual relations are far more 
complicated : the excess of carbonic acid taken up in the polar regions is constantly 
being conveyed to warmer latitudes by 7 the polar currents, to make up for loss of carbonic 
acid constantly suffered by the w T ater there. It may be pointed out that, assuming (as 
we have tacitly done so far) there were no other source of carbonic acid than the 
atmosphere, the sea-water even in the arctic and antarctic circles could not contain more 
than traces of actually free carbonic acid in addition to fully saturated bicarbonate. 
According to Bunsen, one volume of even pure water of 0° 0., when shaken with excess 
of pure carbonic acid of 760 mms. dry gas pressure, absorbs only 1‘8 volumes of the 
gas (measured dry at 0° C. and 760 mms.). Even in the polar regions, the temperature 
of liquid sea-water never sinks by more than 2 or 3 degrees beloAv 0° C., hence the 
maximum proportion of carbonic acid which such polar sea-water could possibly take 
up from the atmosphere may be roughly estimated at 0‘0003 x 1800, or to '54 cubic 
centimetres, or about 1 milligram per litre of water. And supposing at a given place a 
larger proportion were produced by an influx of gas from below 7 , this excess of carbonic 
acid, over and above the 0‘5 c.c., would speedily diffuse out into the atmosphere. 
That there are supplies of carbonic acid in the ocean itself cannot be doubted. 
One of them is afforded by the decay of marine animals and plants ; but this supply, 
although very large, doubtless amounts to very little, wdien compared with the immense 
quantities supplied by the sub-marine volcanic carbonic acid springs which no doubt 
exist at the bottom of the sea as they do on dry land. It is w ; ell known that carbonic 
acid is one of the most abundant after products of volcanic eruptions, and we have good 
evidence for supposing that volcanic eruptions frequently 7 take place over the floor of the 
ocean. If w r e nowhere see these springs coming up in the ocean as jets ot frothy carbonic- 
acid w r ater, such as issue from the earth on dry land, this proves only that the springs do 
not happen to exist in any of the shallow 7 places. And where they 7 do exist at average 
ocean-depths they have no chance of becoming “ springs ” in the strictest sense of the 
