THE GULF STREAM. 41 



and target. Its path would lie in the plane of a gi'eat circle. But 

 there is diurnal rotation ; the earth does revolve on its axis ; and 

 since Beniini is nearer to the equator than Ireland is, the gun 

 would be moving in diiu-nal 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 ri<jM (§ 108) of his mark. In other words, 

 that the path actually described by the ball would be a resultant 

 arising from this difierence in the rate of rotation and the trajectile 

 force. Like a ray of light from the stars, the baU would be 

 affected by aberration. The ball so shot presents the case of the 

 passenger in the raikoad car throwing an apple, as the train sweeps 

 by, to a boy standing by the wayside. 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 natm-al tendency 

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



rents both in the sea ^ n •■•in t ji • • j t •^ t. 



and air to move in 01 all projcctilcs througn the aiT, IS to describe eacn 

 ^S'law.'''''^''^' its cmrve of flight very nearly in the plane of a great 

 circle. The natural tendency of all matter, when put in motion, is 

 to go from point to point by the shortest distance, and it requires 

 force to overcome this tendency. Light, heat, and electricity, the 

 howhng wind, running water, and all substances, whether ponde- 

 rable or imponderable, seek, when in motion, to obey this law. 

 Electricity may be tiurned aside from its course, and so may the 

 cannon-ball or running water ; but remove eveiy obstruction, 

 and leave the ciu:rent or the shot free to continue on in the 

 direction of the first impulse, or to turn aside of its own volition, so 

 to speak, and straight it will go, and continue to go — if on a plane, 

 in a straight line ; if about a sphere, in the arc of a great circle — 

 thus showing that it has no volition except to obey impulse ; and 

 that impulse comes from the physical requirements upon it to take 

 the shortest way to its point of destination. 



121. The waters of the Gulf Stream, as they escape fi'om the 

 This law recognized G-uLf, are bouud for the British Islands, to the North 

 by the Gulf Stream, gea, and Frozeu Ocean (Plate IX.). Accordingly, 

 they take (§118), in obedience to this physical law, the most direct 

 course by which nature will permit them to reach their destination. 



