Page:Physical Geography of the Sea and its Meteorology.djvu/66

40 to show, but observations to prove. Navigators, while drifting along with the Gulf Stream, have lowered a boat to try the surface current. In such cases, the boat would drift either to the east or to the west, as it happened to be on one side or the other of the axis of the stream, while the vessel herself would drift along with the stream in the direction of its course: thus showing the existence of a shallow roof-current from the middle towards either edge, which would carry the boat along, but which, being superficial, does not extend deep enough to affect the drift of the vessel.

111. Drift matter sloughed off to the right.—That such is the case (§ 110) is also indicated by the circumstance that the sea-weed and drift-wood which are found in such large quantities along the outer edge of the Gulf Stream, are rarely, even with the prevalence of easterly winds, found along its inner edge—and for the simple reason that to cross the Gulf Stream, and to pass over from that side to this, they would have to drift up an inclined plane, as it were; that is, they would have to stem this roof-current until they reached the middle of the stream. We rarely hear of planks, or wrecks, or of any floating substance which is cast into the sea on the other side of the Gulf Stream being found along the coast of the United States. Drift-wood, trees, and seeds from the West India Islands, are often cast up on the shores of Europe, but rarely on the Atlantic shores of this country.

112. Why so sloughed off.—We are treating now of the effects of physical causes. The question to which I ask attention is, Why does the Gulf Stream slough off and cast upon its outer edge, sea-weed, drift-wood, and all other solid bodies that are found floating upon it? One cause has been shown to be in its roof-shaped current; but there is another which tends to produce the same effect; and because it is a physical agent, it should not, in a treatise of this kind, be overlooked, be its action never so slight. I allude now to the effects produced upon the drift matter of the stream by the diurnal rotation of the earth.

113. Illustration.—Take, for illustration, a railroad that lies north and south in our hemisphere. It is well known to engineers that when the cars are going north on such a road, their tendency is to run off on the east side; but when the train is going south, their tendency is to run off on the west side of the track—i. e., always on the right-hand side. Whether the road be