un. Thus the Gulf Stream, the northern branch
of the Atlantic tropical current, by flowing into the North Atlantic,
contributes to the temperature of the region within the Arctic Circle
more heat than actually comes to that district by the direct influx
from the sun.

The above statements as to the climatal effect of the ocean streams
show us how important it is to obtain a sufficient conception as to
the way in which these currents now move and what we can of their
history during the geologic ages. This task can not yet be adequately
done. The fields of the sea are yet too imperfectly explored to afford
us all the facts required to make out the whole story. Only in the
case of our Gulf Stream can we form a full conception as to the
journey which the waters undergo and the consequence of their motion.
In the case of this current, observations clearly show that it arises
from the junction near the equatorial line of the broad stream created
by the two trade-wind belts. Uniting at the equator, these produce a
westerly setting current, having the width of some hundred miles and a
depth of several hundred feet. Its velocity is somewhat greater than a
mile an hour. The centre of the current, because of the greater
strength of the northern as compared with the southern trades, is
considerably south of the equator. When this great slow-moving stream
comes against the coast of South America, it encounters the projecting
shoulder of that land which terminates at Cape St. Roque. There it
divides, as does a current on the bows of an anchored ship, a
part--rather more than one half--of the stream turning to the
northward, the remainder passing toward the southern pole; this
northerly portion becomes what is afterward known as the Gulf Stream,
the history of which we shall now briefly follow.

Flowing by the northwesterly coast of South America, the northern
share of the tropical current, being pressed in against the land by
the trade winds, is narrowed, and therefore acquires at once a swifter
flow, the increased speed being due to conditions like those which add
to the velocity of the water flowing through a hose when it comes to
the constriction of the nozzle. Attaining the line of the southeastern
or Lesser Antilles, often known as the Windward Islands, a part of
this current slips through the interspaces between these isles and
enters the Gulf of Mexico. Another portion, failing to find sufficient
room through these passages,