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 
more 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, we 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, mitil we discover it lead- 
ing- us into some palpable absurdity, or until some other hypoth- 
