\i<\ L'^'^ c ON THE SALTNESS 01' THE SEA. r^r 



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In order to comprehend .iright the currents of the sea, and to study with advantage the system of oceanic 

 circulation, it is necessary to understand the effects produced by the salts of the sea upon the equilibrium of 

 its waters ; for wherever equilibrium be destroyed, whether in the air or water, it is restored by mQlion ; and 

 motion among fluid particles gives rise to currents, which in turn, constitute circulation. The question is 

 often asked, " why is the sea salt? " I want to show that the circulation of the ocean depends, in a great 

 measure, upon the salts of sea water. 



As a general rule, the sea is of a uniform degree of saltness and the constituents of sea water are as 

 constant in their properties and as uniform in tlieii proportions, as are the components of the atmosphere. 



We sometimes come across arms of the sea, or places in the ocean, where we find the water more salt 

 or less salt than sea water is generally ; but this circumstance is due to local causes of easy explanation. For 

 instance : When we come to an arm of the sea, as the Red Sea, where it never rains, and where the at- 

 mosphere is continually abstracting, by evaporation, fresh water from the salt, we may naturally expect to 

 find a greater propoition of salt in the sea water that remains, than we do near the mouth of some great 

 river, as the Amazon ; or in the regions of constant precipitation, or other parts, where it rains more than it 

 evaporates : and though therefore we do not find sea water from all parts of the ocean actually of the same 

 degree of saltness, yet we do find, as in the case of the Red Sea, sea water that is continually giving off to 

 evaporation fresh water in large quantities ; nevertheless, for such water, there is a degree and a very moderate 

 degree of saltness which is a maximum ; and we moreover find, that though the constituents of sea water, like 

 those of the a'mosphere, are not for every place invariably the same as to their proportions, yet they are the 

 same or nearly the same as to their character. 



When therefore we take into consideration the fact, that as a general rule, sea water is, with the excep- 

 tion above stated, every where and always the same, we find grounds on whicli to base the conjecture, that 

 the oceanic circulation is accoiding to a system which is probably as complete, and as certain in its opera- 

 tions, as is the circulation of the atmosphere from pole to pole, or the circulation of blood through its appointed 

 channels. 



In order to investigate the currents of the sea, and to catch a glimpse of the laws by which they are 

 :,.>verned, hypothesis, in the present meagre state of absolute knowledge with regard to them, seems to be as neces- 

 sary to progi ess, as is a corner stone to a building. To make progress with such investigations, we wantsorne- 

 il;ing to build upon. In the absence of facts we are sometimes permitted to suppose them ; only, in making the 

 selec'.icMi of tlie \arifus hypotheses which are suggested, we are bound to pY-^f- •'- ■! n-,o by which the greatest 



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