11 
underneath, there is a general movement of Polar water towards the Equa* 
torial area, which depresses the temperature of the great oceanic basins 
nearly to the freezing point. Deep sea bottom temperature soundings in the 
Indian Ocean, and on the American side of the Atlantic, confirm this 
view. 
The speaker then described the investigations which had been made, 
in the first instance by himself, and subsequently by Mr. Hunter and Mr. 
P. H. Carpenter, into the gases dissolved in the sea water at various 
depths, and into the existence of organic matter in the water. The sam- 
ples were obtained by the apparatus before described, and were always 
analysed without delay. The gases were expelled from the water by 
boiling, and collected over mercury, after the method of Dr. W. A. Miller. 
The adaptation of his apparatus to the requirements of shipboard was first 
made by the speaker, and was used without alteration by his successors. 
The mixed gases, confined over mercury, were treated with caustic potash, 
which removed the carbonic acid ; the oxygen^was next absorbed by the 
addition of pyrogallic acid, and the remainder was taken as nitrogen. 
The first point of importance established was, that the total amount of 
gas dissolved in the sea water did not vary with the depth. It had been 
supposed, that the excessive pressure at great depths caused the water 
there to hold a large quantity of gas in solution, but there was no evidence 
whatever of this being the case, the total volume of gas in sea water, at 
whatever depth, being about 2*8 vols, from 100 vols, of water. No doubt 
the pressure at great depths was sufficient to retain much more than this 
if the gas were forced into the water, but in the opinion of the speaker 
there was no satisfactory hypothesis to account for the means by which 
the extra volume of gas could be forced in ; at any rate, as a matter of 
fact, it was not there. 
The general average of 30 analyses of* the gases in surface-water was as 
follows : — 
Per Cent. 
Oxygen - - - 25-046 
Nitrogen -• - - 54-211 
Carbonic Acid - 20*743 
100-000 
N.B. — In all cases the results are reduced to 0° Cent, and 760 mm. 
barometric pressure, (32° Fah., and 30*0 inches nearly). 
It was observed, however, that during, and immediately after, strong 
Proportion. 
100 
216 
83 
