"but, as I have often told you, he
brings about his purposes by the laws or causes which he himself has
established. There may be several causes in operation to form this
ocean-stream, though up to this moment learned men have been unable to
decide what they are. Now one theory is advanced, now another. The
shape of the Gulf Stream may have something to do with it. It appears
that it is higher than the rest of the surface, for it is more bulky.
Water will always seek its level. It has thus a tendency to flow
towards the colder and lower water of the poles, feeling at the same
time the effect of the diurnal motion of the globe; while the water of
the poles, to supply its place, flows towards the equator, subject to
the same disturbing cause. Thus the water of the globe is set in
motion. These being hot, tropical waters, remain on the surface, and a
portion of them is forced into the Gulf of Mexico. Here, though they
lose somewhat of their saltness from the fresh waters of the Mississippi
and Orinoco, they gain more heat from these hot streams, and are still
much Salter than the rest of the ocean. Perhaps the impetus may be
given them by the pressure of the currents from the poles. The diurnal
motion of the globe will account for the drift-wood and sea-weed being
cast off on the east or left bank of the stream. There is another cause
for this. From the stream being roof-shaped, any drift which its left
portion took up would have to go up hill to get to the northward.
Therefore, though trees and other produce of the West Indies are found
on the shores of Europe, none are ever picked up on those of America.
And this brings me to the point from which I set out--the cause of the
Sargasso Sea, the centre, it may be called, of this wondrous and almost
inexplicable Gulf Stream."

"But, father, still you have not told us why the Gulf Stream flows in
the direction it does," said Gerard, who generally stuck to the point in
an argument on which he wanted information.

"Men possessed of far more scientific knowledge than I can boast of,
have been puzzled to reply to that question," returned the captain.
"The trade-winds, the diurnal motion of the earth, the expansion of
water by heat, may all combine to force it along and direct its course;
and yet there may be some still more potent cause at work unperceived by
us, perhaps undiscoverable. One thing we know, that it was the will of
the Almighty that so it should flow,