Il8 LIGHT SCIENCE FOR LEISURE HOURS. 



The point on which most stress is placed is the 

 shallowness of the passage called the ( Bernini Narrows/ 

 through which it is assumed that the whole of the Gulf 

 current must pass. This passage has a width of about 

 forty miles, and a depth of little more than six hundred 

 yards. The current which flows through it is perhaps 

 little more than thirty miles in width, and a quarter of 

 a mile in depth. It is asked with some appearance of 

 reason, how this narrow current can be looked upon as 

 the parent of that wide stream which is supposed to 

 traverse the Atlantic with a mean width of some five 

 or six hundred miles. Indeed, a much greater width 

 has been assigned to it, though on mistaken grounds ; 

 for it has been remarked that since waifs and strays 

 from the tropics are found upon the shores of Portugal, 

 as well as upon those of Greenland, we must ascribe 

 to the current a span equal to the enormous space 

 separating these places. But the circumstance here 

 dwelt upon can clearly be explained in another way. 

 We know that of two pieces of wood thrown into the 

 Thames at Richmond, one might be picked up at 

 Putney, and the other at Gravesend. Yet we do not 

 conclude that the width of the Thames is equal to the 

 distance separating Putney from Gravesend. And 

 doubtless the tropical waifs which have been picked up 

 on the shores of Greenland and of Portugal have 

 found their way thither by circuitous courses, and not 

 by direct transmission along opposite edges of the 

 great Gulf current. 



But certainly the difficulty associated with the nar- 



