426 APPENDIX, 



absolute inequality in the saltness of the water in 

 general. To give a decided opinion on it, the 

 sea water must be fetched up from considerable 

 depths, and weighed. Probably the greater salt- 

 ness arises from the rapid decrease of the fresh 

 water, in consequence of evaporation. From the 

 well known slowness of the transition of chemical 

 elements in undisturbed compounds, this decrease 

 is but slowly repaired ; and as the upper layers are 

 also the warmer, they may, notwithstanding their 

 greater specific density, in consequence of their 

 extent, be maintained by the warmth swimming 

 above the lower cooler layers, by which a principal 

 agent of commixture, the difference of weight, 

 is rendered of no effect. This slowness of change, 

 and the condensation of the saline solution at the 

 surface, which results from it, has the advantage, 

 that the acceleration of the evaporation sets 

 bounds to itself, because, with the increasing con- 

 densation, the attraction of the salt to the parts 

 of the water is greater, and, consequently the 

 diminution of the latter less. Without this arrange- 

 ment, the tropical seas would perhaps be covered 

 like the frozen seas of the north, with constant 

 fogs. Subsequent experiments will show how far 

 our explanation of this inequality is correct ; of 

 which we have now more hopes, as convenient 

 accurate apparatus have been discovered to fetch 

 u}) water from any depth, at pleasure, and un- 

 mixed. 



