228 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY. 



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

 sea in the Arctic Ocean. 



463. As a general rule, the constituents of sea water are as 

 Uniform character coustaut iu their proportious as are the components 

 of sea water. q£ ^^^q atmosphcrc. It is truo that 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 Ked Sea 

 (§ 376), upon which it never rains, and from which the atmo- 

 sphere 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 Ked Sea, and all such natural salt-pans, as that and 

 other rainless portions of the sea may be called, there is, on account 

 of currents which are continually bearing away the water that has 

 given off its vapours and bringing forward that which is less con- 

 centrated as to brine, a moderate degree of saltness which its 

 waters cannot exceed. We moreover find that, though the con- 

 stituents 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 always the same, and that it can only be made so by being 

 well shaken together, we find grounds on which to base the con- 

 jecture that the ocean has its system of circulation, which is well 

 calculated to excite our admiration, for it is as wonderful as the 

 circulation of the blood. 



464. In order to investigate the effect of the salts of the sea 

 Hypotheses. upon its currcuts, and to catch a glimpse of the 



laws by which the circulation of its waters is governed, hypothe- 



* The great American lakes afford, it may bo supposed, a considerable portion 

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

 are. Visiting the Lake country in 1858, I was struck with tlie 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 Underwriters, I was in- 

 formed 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 ! 



