American Association. 277 



bodies is opposed to all known principles. It is to be hoped, 

 therefore, that those who still feel inclined to adopt and maintain 

 this theory of convenience, will not forget to enlighten ns as to 

 the cause of the peculiar departure from known laws exemplified 

 in the cases under review." 



QUESTIONS CONNECTED WITH THE SALTNESS OF THE SEA, 



A second paper by Professor Chapman, related to the use of 

 the Saltness of the Sea. This is a subject of vyhich too narrow 

 views should not be taken, since it is easy to perceive many im- 

 portant uses secured by the substances held in solution in the 

 ocean. Professor Chapman brought forward an interesting ex- 

 periment, illustrative of the equal diffusion of this saline matter, 

 under circumstances unfavourable to transference of the water 

 itself; and leading to the conclusion that one important conse- 

 quence of the saltness of the sea is the regulation of the rate of 

 evaporation from its surface. 



"It is a current opinion that, in consequence of the surface of the 

 sea becoming Salter and hence heavier by evaporation, a down- 

 ward motion of the surface water necessarily takes place ; and 

 hence Lieutenant Maury's hypothesis that the sea is salt in order 

 to produce circulation. Some time ago I suggested another object 

 in explanation of the saltness of the sea, viz. : that the sea is salt 

 in order to regulate evaporation. The greater the amount of salt, 

 the slower the evaporation of the water, — and the reverse : so 

 that, if by any easily conceivable cause, or combination of circum- 

 stances, the normal degree of saltness becomes either increased or 

 diminished — a kind of self-regulating force is set up to resist the 

 continuation of the abnormal action, until time restore the balance. 

 Even leaving out of consideration the equalizing effects produced 

 by the accession of fresh vs^ater to the surface of the sea by rain 

 and rivers, it seemed to me that the principle of diffusion was in 

 itself sufficient to prevent the sinking of the water thus affected by 

 evaporation ; or, at least, to prevent the sinking of this water to 

 any extent. But how to prove the point. The fact that the salt- 

 ness of the open sea was substantially the same at considerable 

 depths and at the surface, says nothing ; as it would necessarily 

 follow, that for every heavy particle of water that sunk, a lighter 

 particle would rise up to supply its place ; and hence the com- 

 position of the water would be kept uniform, without the prin- 

 ciple of diffusion being in any way required to explain the phe- 



