PRESIDENTIAL ADDRESS. 



in the mechanical qualities of the materials of which the 

 oceanic floor is composed ; and, lastly, in the food supply. 



As determined by physicists and chemists the water of the 

 deep sea varies in the proportions of mineral salts, carbonic 

 acid and air contained in it very much as does the surface 

 water. In general at the surface the warmer water of the 

 tropics has the more salt and the less nitrogen. When carried 

 by currents to the Polar regions, and cooled, this tropical wat.r 

 sinks to the bottom carrying its excess of salt along with it. 

 The Polar waters are less saline and contain more nitrogen. 

 The proportion of atmospheric air in the water is found strictly 

 related to the temperature, the pressure at great depths being 

 regarded as having no bearing on the question. The amount of 

 oxygen in the sea water diminishes gradually as we descend 

 from the surface until about 350 fathoms is reached, when it 

 ceases to change or at most increases slightly until the bottom 

 is attained. 



Carbonic acid, according to Tornoe, does not exist in a free 

 state in sea water, but only in the form of carbonates or to a less 

 degree of bicarbonates. Unless the decomposition of animal 

 matter in some manner sets free the carbonic acid, this con- 

 clusion is one which cannot be adopted without question, espe- 

 cially when we consider the great difficulties which are en- 

 countered in any attempt to obtain, or when obtained to ana- 

 lyze, abyssal water. ■ The effect of erosion on the shells dredged, 

 from the deeps, even when they contain the living animal, is 

 so strongly marked, the devices for protection against erosion 

 are so recognizable in various species, that the biologist may 

 well call the physicist to a halt, while the latter re-examines his 

 data. It is certain that erosive agencies, of which the effects 

 are indistinguishable from those known to be due to carbonic 

 acid in other instances, are extremely active in the deeps. 



