THE SALTS OF THE SEA. 151 



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 (^ 238), upon which it never rains, and 

 from which the atmosphere is continually abstracting, by evapor- 

 ation, fresh water from the salt, we may naturally expect to find 

 a greater proportion 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 

 toore than it evaporates. Therefore we do not find sea water 

 from all parts of the ocean actually of the same degree of salt- 

 ness, 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 quan- 

 tities ; nevertheless, for such water there is a degree, and a very 

 moderate degree, of saltness which is a maximum ; and we more- 

 over find that, though the constituents of sea water, like those of 

 the atmosphere, 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. 



290. When, therefore, we take into consideration the fact that, 

 as a general rule, sea water is, with the exceptions above stated, 

 every where and always the same, and that it can only be made 

 so by being well shaken together, we find grounds on which to 

 base the conjecture that the ocean has its system of circulation, 

 which is probably as complete and not less wonderful than is the 

 circulation of blood through the human system. 



In order to investigate the currents of the sea, and to catch a 

 glimpse of the laws by which the circulation of its waters is gov- 

 erned, hypothesis, in the present meagre state of absolute knowl- 

 edge with regard to the subject, seems to be as necessary to prog- 

 ress as is a corner-stone to a building. To make progress with 

 such investigations, we want something to build upon. In the ab- 

 sence of facts, w^e are sometimes^permitted to suppose them ; only, 

 in supposing them, we should take not only the possible, but the 

 probable ; and in making the selection of the various hypotheses 

 which are suggested, we are bound to prefer that one by which 

 the greatest number of phenomena can be reconciled. When we 

 have found, tried, and offered such an one, we are entitled to claim 

 for it a respectful consideration at least, until we discover it lead- 

 ing us into some palpable absurdity, or until some other hypoth- 



