153 
THE PHYSICAL GEOGRAPHY OF THE SEA, 
esis be suggested which will account equally as well, but for a 
greater number of phenomena. Then, as honest searchers after 
truth, we should be ready to give up the former, adopt the latter, 
and to try it until some other better than either of the two be of- 
fered. 
291. With this understanding, I venture to olFer an hypothesis 
with regard to the agency of the salts or solid matter of the sea 
in imparting dynamical force to the waters of the ocean, and to 
suggest that one of the purposes which, in the grand design, it was 
probably intended to accomplish by having the sea salt, and not 
fresh, was to impart to its waters the forces and powers necessary 
to make their circulation complete. 
In the first place, we do but conjecture when we say that there 
is a set of currents in the sea by which its waters are conveyed 
from place to place with regularity, certainty, and order. But 
this conjecture appears to be founded on reason ; for if we take a 
sample of water which shall fairly represent, in the proportion of 
its constituents, the average water of the Pacific Ocean, and ana- 
lyze it, and if we do the same by a similar sample from the At- 
lantic, we shall find the analysis of the one to resemble that of the 
other as closely as though the two samples had been taken from 
the same bottle after having been well shaken. How, then, shall 
we account for this, unless upon the supposition that sea water 
from one part of the world is, in the process of time, brought into 
contact and mixed up with sea water from all other parts of the 
world ? Agents, therefore, it would seem, are at work, which 
shake up the waters of the sea as though they were in a bottle, 
and which, in the course of time, mingle those that are in one part 
of the ocean with those that are in another as thoroughly and com- 
pletely as it is possible for man to do in a vessel of his own con- 
struction. 
292. This fact, as to uniformity of components, appears to call 
for the hypothesis that sea water which to-day is in one part of 
the ocean, will^ in the process of time, be found in another part 
the most remote. It must, therefore, be carried about by cur- 
rents ; and as these currents have their offices to perform in the 
terrestrial economy, they probably do not flow by chance, but in 
obedience to physical laws ; they no doubt, therefore, maintain 
the order and preserve the harmony which characterize every de- 
