38 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOriOLOGY. 



water, figures show that the middle or axis of the GuK Stream 

 there should be nearly two feet higher than the contiguous waters 

 of the Atlantic. Hence the surface of the stream should present a 

 double inclined plane, from which the water would be running down 

 on either side as from the roof of a house. As this runs off at the 

 top, the same weight of colder ^vater runs in at the bottom, and so 

 raises up the cold-water bed of the Gulf Stream, and causes it to 

 become shallower and shallower as it goes north. That the G-ulf 

 Stream is therefore roof-shaped, causing the waters on its smface to 

 flow off to either side from the middle, we have not only circum- 

 stantial evidence to shov\^, but observations to prove. Navigators, 

 while druting along with the Gulf Stream, have lowered a boat to 

 try the surface cmTcnt. 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 com'se : thus shovf ing 

 the existence of a shallow roof-ciu'rent from the middle towards either 

 edge, which would carry the boat along, but which, being superfi- 

 cial, does not extend deep enough to affect the drift of the vessel. 



111. That such is the case (§ 110) is also indicated by the cir- 

 Drift matter slough- cumstauce that the sea- weed and drift-wood which 

 ed off to the right, ^^.g fouud 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-cm'rent 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 GuK 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 Em'ope, but rarely on the 

 Atlantic shores of this country. 



112. AVe are treating now of the effects of physical causes. The 

 Vviiy so sloughed off. 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 sho^^m 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 



