§ 118-120. THE GULF STREAM. 39 



ill the open sea has the water been found to deepen so suddenly 

 as here. Coming from the north, the bottom of the sea is shelv- 

 ing ; but suddenly, after passing these Banks, it dips down by a 

 precipitous descent to unknown depths — thus indicating that the 

 debris which forms the Grand Banks comes from the north. 



118. From the Straits of Bemini the course of the Gulf Stream 

 The Gulf stream de. (Blatc YI.) dcscribcs (as far as it can be traced over 

 tSfpSh'/aV'^jec't^ toward the British Islands which are in the midst 

 ^'^^ of its waters) the arc of a great circle nearly. Such 

 a course as the Gulf Stream takes is very nearly the course that 

 a cannon ball, could it be shot from these straits to those islands, 

 would follow. 



119. If it were possible to see Ireland from Bemini, and to get 

 Its path from Bern- ^ cannou that would reach that far, the person stand- 

 ini to Ireland. ^^^g ^^^ Bcmiui and taking aim, intending to shoot 

 at Ireland as a target, would, if the earth were at rest, sight di- 

 rect, and make no allowance for difference of motion between 

 marksman and target. Its path would lie in the plane of a great 

 circle. But there is diurnal rotation ; the earth does revolve on 

 its axis ; and since Bemini is nearer to the equator than Ireland 

 is, the gun woald be moving in diurnal rotation (§ 91) faster than 

 the target, and therefore the marksman, taking aim point blank 

 at his target, would miss. He would find, on examination, that 

 he had shot south — that is, to the right (§ 103) of his mark. In 

 other words, that the path actually described by the ball would 

 be a resultant arisins; from this difference in the rate of rotation 

 and the trajectile force. Like a ray of light from the stars, the 

 ball would be affected by aberration. The ball so shot presents 

 the case of the passenger in the railroad car throwing an apple, 

 as the train sweeps by, to a boy standing by the way-side. If he 

 throw straight at the boy, he will miss, for the apple, partaking 

 of the motion of the cars, will go ahead of the boy, and for the 

 very reason that the shot will pass in advance of the target, for 

 both the marksman and the passenger are going faster than the 

 object at which they aim. 



120. Hence we may assume it as a law, that the natural tend- 

 Tendency of all cur- eucv of all currcuts in the sea, like the natural 



rents both in the sea % ^ .. .mi 7 i • • ^ J 



and air to move in tendeucv of all proiectilcs through the air, is to ue- 



greit circles a phys- ., "^ , . ^ p n • 1 . i • xT, 



icaiiaw. scribc cach its curve 01 night very nearly m tne 



