THE SALTS OF THE SEA. 237 



waters of the ocean, the sound of thunder -would scarce be heard 

 in the sky* — there would be no Gulf Stream, and no open sea in 

 the Arctic Ocean. 



463. Uniform character of sea ivater. — As a general rule, the 

 constituents of sea water are as constant in their proportions as 

 are the components of the atmosphere. It is true that we some- 

 times 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 Eed Sea (§ 376), upon which it never rains, and from 

 which the atmosphere is continually abstracting, by evaporation, 

 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 in other parts, as on the polar 

 side of 40^ in the North Atlantic, where it rains more than it 

 evaporates. Yet in the case of the Red Sea, and all such natural 

 salt-pans, as that and other rainless piortions of the sea may be 

 called, there is, on accoiTnt of currents which are .continually 

 bearing away the water that has given off its vapours and bringing 

 forward that which is less concentrated as to brine, a moderate 

 degree of saltness which its waters cannot exceed. We moreover 

 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. When , therefore, we take into consideration the 

 fact that, as a general rule, sea water is, with the exception above 

 stated, everywhere and alwaj^s 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 cir- 

 culation, which is well calculated to excite our admiration, for it 

 is as wonderful as the circulation of the blood. 



* The great American lakes afford, it may be supposed, a considerable por- 

 tion of the vapour which goes to make rain for the hydrographic basin in whicli 

 they are. Visiting the Lake country in 1858, 1 was struck with the fact that 

 so few trees bore the marks of lightning. The rule appeared to be, the nearer 

 the lakes, the more rare was it for one of these ornaments of the forest to have 

 been defaced by lightning ; and, on inquiry from the Lake Board of Under- 

 writers, I was informed that among the records of lake disasters there was not 

 a single instance of a vessel having been struck by lightning on the North 

 American lakes ! 



