“I shall take a sight of the sun presently, my boy,” he answered, with one of his odd winks, giving a quizzical glance at Mr Marline, as if telling me he thought he had shut him up for the time; “then I shall be better able to tell you. However, as we’ve been running twelve knots an hour good since four bells in the first watch, we ought to have made over a hundred miles or so from our last stopping place.”
“And where shall we get to if we continue running on the same as now?” I next inquired, thinking of what Mr Marline had said.
“To the Banks of Newfoundland, I suppose, if the same wind holds; but, I’m of opinion that we’ll have a change as soon as we fetch the Gulf Stream, when we shall be able to shape a straight course for the Channel.”
“And what is the Gulf Stream, captain?” I then asked.
“Bless the boy!” he exclaimed, “I never saw such a chap for questions; why, you’re almost as bad as Mr Marline! Well, if you must know, the Gulf Stream, or ‘Florida Current’ as it is frequently called, is something very like a river of warm water, some eighty to three hundred miles wide, flowing through the surrounding ocean from the Gulf of Mexico to Europe in a circular nor’-east by east direction. Starting from between the Dry Tortugas and Cuba, it skirts the eastern shores of the United States, then passing across the Atlantic to the south of the Banks of Newfoundland, where it branches off into two currents in mid ocean, near the Azores. One of these streams steers north, along the shores of Norway, while the other leg sweeps onward to the English Channel, circling round the Bay of Biscay and then pursuing a southerly course along the Spanish coast until it meets the great equatorial current coming up from the south Atlantic. Uniting now with this, the double current flows back westwards to the place of its birth, only to renew its onward course again from the Caribbean Sea.”
“But what causes it?” I said.
“Well, that is a disputed point,” replied the captain. “One authority says that the Gulf Stream ‘is caused by the motion of the sun in the ecliptic,’ and I think there is a good deal of reason in this. Another philosopher puts it down to the influence of the anti-trade and passage winds blowing from the west to the east along the zone in which the stream travels; and I think much might be said about that argument, especially as the westerly current south of the tropic of Cancer is undoubtedly caused by the trade-wind. A third scientific gentleman ascribes the stream to the fact, that the earth being a globe, the water on the equator is higher than that of the tropics, and the lower stratum of fluid circles round constantly in its endeavour to reach into the bigger volume beyond its reach; but I can’t say much for this theory myself, Tom.”
“But how do you know the Gulf Stream from the rest of the ocean?” I here asked.
“As easily as you can distinguish a marlinespike from a capstan-bar,” answered Captain Miles. “It is not only bluer than the surrounding water, through which it flows, as I’ve told you, like a river, but it is also several degrees warmer; for, when a ship is close to the stream and sailing in the same direction in which it is running, a bucket of water dipped from the sea on one side of the vessel will show an appreciable difference of temperature to that procured from the other. Besides, my boy, there’s the Gulf-weed to tell you when you are within the limits of the current; however, you’ll see lots of the weed by and by, no doubt, before we finish our voyage.”
“You said, captain,” I observed, “that the great currents of the ocean are produced by the trade-winds?”