THE GULF STREAM. 39 



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 shght. I allude novv^ to 

 the effects (upon the drift matter of the stream) produced by the 

 diurnal rotation of the earth. 



43. Take, for illustration, a rail-road that runs north and south. 

 It is well known to engineers, that when the cars are going north 

 on such a road, their tendency is to run off on the east side ; but 

 when the train is going south, their tendency is to run off on the 

 west side of the track — i. e., always on the right-hand side. 

 Whether the road be one mile or one hundred miles in length, the 

 effect of diurnal rotation is the same, and the tendency to run off, 

 as you cross a given parallel at a stated rate of speed, is the same, 

 whether the road be long or short, the tendency to fly the track 

 being in proportion to the speed of the trains, and not at all in 

 proportion to the length of the road. 



44. Now^, vis inerticB and velocity being taken into the account, 

 the tendency to obey the force of this diurnal rotation, and to trend 

 to the right, is proportionably as great in the case of a patch of 

 sea-weed as it drifts along the Gulf Stream, as it is in the case 

 of the train of cars as they speed to the north, along the iron track 

 of the Hudson River railway, or the Great Western railway of 

 England. 



The rails restrain the cars and prevent them from flying off; 

 but there are no rails to restrain the sea-w^eed, and nothing to pre- 

 vent the drift-matter of the Gulf Stream from going off in obedi- 

 ence to this force. The slightest impulse tending to turn aside 

 bodies moving freely in water is immediately felt and implicitly 

 obeyed. 



45. It is in consequence of this diurnal rotation that drift-w^ood 

 coming down the Mississippi is so very apt to be cast upon the 

 west or right bank. This is the reverse of what obtains upon the 

 Gulf Stream, for it flows to the north ; it therefore sloughs off to 

 the east. 



The effect of diurnal rotation upon the winds and upon the cur- 

 rents of the sea is admitted by all — the trade-winds derive their 

 easting from it — it must, therefore, extend to all the matter which 

 these currents bear with them, to the largest iceberg as well as 

 to the merest sprig of grass that floats upon the w^aters, or the 



