THE GULF STREAM. 27 



82. TJie Bonifaccio current. — That the winds do make ciirrents 

 in the sea no one will have the hardihood to deny : but currents 

 that are born of the winds are as unstable as the winds ; tin- 

 certain as to time, place, and direction, they are sporadic and 

 ephemeral ; they are not the constant currents such as have been 

 already enumerated. Admiral Smyth, in his valuable memoir on 

 the Mediterranean (p. 1G2), mentions that a continuance in the 

 Sea of Tuscany of " gusty gales " from the south-west has been 

 known to raise its surface no less than twelve feet above its 

 ordinary level. This, he says, occasions a strong surface drift 

 through the Strait of Bonifaccio. But in this we have nothing 

 like the Gulf Stream; no deep and narrow channel-way to 

 conduct these waters off like a miniature river even in that sea, 

 but a mere surface flow, such as usually follows the piling up of 

 water in any pond or gulf above the ordinary level. The Boni- 

 faccio current does not flow like a " river in the sea " across the 

 Mediterranean, but it spreads itself out as soon as it passes the 

 Straits, and, like a circle on the wa,ter, 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. Tlie heel of the Gulf Stream an ascending plane. — Supposing 

 with Franklin, and those of his school, that the pressure of 

 the waters that are forced into the Caribbean Sea by the trade- 

 winds is the sole cause of the Gulf Stream, that sea and the 

 Mexican Gulf should have a much higher level than the 

 Atlantic. Accordingly, the advocates of this theory require for 

 its support " a great degree of elevation." Major Eennell 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 approximation, the velocity and 

 breadth of the same waters off Cape Hatteras. Their breadth 

 here is about seventy-five miles against thirty-two in the 

 " Narrows " of the Straits, and their mean velocity 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 oi descending, 

 its bed represents the surface of an inclined plane — inclined 

 downwards from the north towards the south — «jj which plane the 

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



