The currents of the oceans are amazing. They are a study all by themselves. One of the first things that impressed the author is their permananance. Their primary driving power is the wind, and the modifying forces are the sun, the revolving of the earth ever towards the east, and the obstructing masses of the continents.
The surface of the sea is heated by the sun unequally, the warmer water expands and becomes lighter, while the cold water becomes heavier and more dense. Probably this brings about a slow exchange of water between the Poles and the equator.
The currents can be quite strong. Take the Gulf Stream, for example. A Spanish ship with the trade winds at her back was pushed back when in the current. The Rode Island merchant ships knew this current, so they got back faster than the English mail ships, who did not know where it was, or how to make headway against it. Benjamin Franklin, when he was postmaster, received a complaint about this speed difference between the ships, and so, perplexed, he asked a Nantucket sea captain. The sea captain told Franklin the reason (the difference of knowledge above), and Franklin asked him to mark the current on a map.
If you ever wonder why the water is so cold at some seaside resorts, remember that the water of the Labrador current is between you and the Gulf Stream.
Bell
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