24: THE PHYSICAL GEOGRAPHY OF THE SEA. 



on the water, loses itself by broad spreading as soon as it finds 



sea room. As soon as the force that begets it expends itself, the 



current is done. 



83. Supposing, with Franklin, and those of his school, that the 



The bed of the Gulf prcssurc of the watcrs that are forced into the Car- 

 stream an ascend- ... r-<i ^ , -\ • '^ • ^ i r> 



ing plane. ibbcan iSesi by the trade-winds is the sole cause oi 



the Gulf Stream, that sea and the Mexican Gulf should have a 

 much higher level than the Atlantic. Accordingly, the advo- 

 cates of this theory require for its support "a great degree of ele- 

 vation." Major Rennell likens the stream to "an immense river 

 descending from a higher level into a plain." Now we know 

 very nearly the average breadth and velocity of the Gulf Stream 

 in the Florida Pass. We also know, with a like degree of ap- 

 proximation, the velocity and breadth of the same waters off Cape 

 Ilatteras. Their breadth here is about seventy -five miles against 

 thirty -two in the "Narrows" of the Straits, and their mean veloc- 

 ity is three knots off Hatteras against four in the "Narrows." 

 This being the case, it is easy to show that the depth of the Gulf 

 Stream off Hatteras is not so great as it is in the " Narrows" of 

 Bemini by nearly 50 per cent., and that, consequently, instead of 

 descending^ its bed represents the surface of an inclined plane — 

 inclined from the north toward the south — up which plane the 

 lower depths of the stream must ascend. If we assume its depth 

 off Bemini'^ to be two hundred fathoms, which are thought to be 

 within limits, the above rates of breadth and velocity will give 

 one hundred and fourteen fathoms for its depth off Hatteras. 

 The waters, therefore, which in the Straits are below the level of 

 the Hatteras depth, so far from descending^ are actually forced up 

 an inclined plane, whose submarine ascent is not less than ten. 

 inches to the mile. 



8J:. The Niagara is an "immense river descending into a plain." 

 The Niagara. But iustcad of preserving its character in Lake On- 

 tario as a distinct and well-defined stream for several hundred 

 miles, it spreads itself out, and its waters are immediately lost in 

 those of the lake. Why should not the Gulf Stream do the 

 same? It gradually enlarges itself, it is true; but, instead of 



* The superintendent reports that the officers of the Coast Survey have sounded 

 with the deep-sea lead, and ascertained its depth here to be 370 fathoms (January, 

 185G). 



