142 



THE CABINET OF NATURAL HISTORY, 



REPLY TO SPORTSMAN'S REJOINDER. 



Messrs. Editors: — Your Correspondent, the " Spoi-ts- 

 man," certainly deserves much credit for his ingenuity in 

 discovering the assailahle points in my argument, and I 

 acknowledge there may be much truth in some parts of his 

 reply — but I regret he has not comprehended my diagram, 

 and on this miscomprehension, has founded a system of 

 reasoning and proof entirely irrelevant to the case. In my 

 explanation of the problem, I supposed Ihat one second of 

 time might elapse from the commencement of pulling the 

 trigger to the arrival of the load, which we will presume, 

 to simplify the case, to be a ball, at the muzzle. This, I 

 imagine, would not be much out of the way, for a sensible 

 interval of time does ensue, after the finger begins to press 

 the trigger, before the load issues from the barrel. When 

 it has arrived at the very muzzle, and that muzzle siill 

 hearing full on the object, is the instant that my principle 

 commences, the preceding being a mere introduction to 

 the case. Let us imagine the gun and the object to be sta- 

 tionary, the ball will of course pass straight from one to 

 the other. Let us suppose the bird alone to be in motion, at 

 .S7 feet in the second, the ball will necessarily, if it take a 

 second to fly from the gun to where the bird was at the mo- 

 ment of discharge, be 87 feet behind the bird. The ball 

 has in this case but one motion, and that a forward one. 

 We will now in addition give it a lateral force. The 

 gun, of course, is useless to the load after it has issued, 

 and its movement may therefore cease. The ball depends 

 for its forward projection, on the powder, and for its late- 

 ral power, on the motion of the gun, and on no other pos- 

 sible cause. Suppose the ball be thrown from a mere hol- 

 low and no barrel to exist, it would necessarily go straight 

 forward from its chamber to the point toward which it was 

 directed. If we give it a tube to pass through, up to the 

 very object itself, it will reach the object it is true, but 

 every inch it travels the route, it is receiving from this 

 passage a lateral force which increases from the chamber, 

 which we will take for the centre of motion, to the end, be- 

 ing from a unit to 87 ft. in the second. During tlie passage of 

 the ball through a tube thus in motion, it will, whilst in the 

 canal, perform a portion of an elipse — somewhat on the same 

 principle that a hoAy projected into the air will do it, to re- 

 turn to thesame point from whence it started — beingcaused 

 in one case, by the lateral pressure of the tube, and in the 

 other, the attraction of gravitation, being in tlie latter in- 

 stance a variable power, acting every instant in a different 

 line according to the point over which the object is passing. 

 In the case in dispute, the ball, so soon as it issues from the 

 barrel, will pass in a right line, because gravitation is not 

 considered, and the projectile has received alltheforces that 

 can influence it. The ' Sportsman' does not object to the 



swing of the muzzle of an ordinary gun being 10 feet in the 

 second; or he may take any distance he may choose, for, a 

 principle that is " philosophicalli/ correct," cannot be inva- 

 lidated by a change of proportion alone. When the ball has 

 therefore arrived at the end of the barrel, itwill have passed 

 through a given distance from the centre of motion, and ac- 

 quired the sole lateral power of the part to which it may be 

 at the instant attached, and if it remain attached, and the 

 muzzle perform a circle, would arrive at the same point 

 again, in a time exactly according to the rate of motion of 

 the part to which it was fixed. We will however let it loose 

 during some part of the revolution, and how fast it will go, 

 allowing it has received no impulse other than the circula- 

 tory motion of the part. Certainly not more rapidly than 

 the source of its motion, the muzzle, exactly as in "Sports- 

 man's" case of a man on a fleet horse, the object thrown, 

 possessing precisely the same forward momentum, and re- 

 turning by the power of gravitation to his hand, — or in the 

 sailing ship, the object retaining a certain force parallel to 

 the surface of the earth, besides the downward gravitation, 

 and arriving at the Jbot of the mast, simply, because the 

 foot of the mast is travelling at the sa77ie identical rate that 

 the head is, and the falling body possessing precisely the 

 same momentum. Please tell me, Messrs. Editors, where 

 the parallelism can be, between these instances of" Sports- 

 man" and the shooting, for he certainly proves by them, 

 that a projected body receives the lateral momentum of the 

 part from whence it issues, and no more. In bis illustra- 

 tions, he forgets that every point and body considered, are 

 moving at the samerate — whereas, in theshootingproblem, 

 the breech of the gun may be supposed a fixed- centre of 

 motion, around wliich the other bodies are revolving, and 

 each possessing a diflerent rapidity in proportion to its dis- 

 tance from the centre. Let me take another instance of the 

 "Sportsman," for I certainly desire to afford him every 

 advantage in my power. We will allow, the surface of tlie 

 earth moves at the rate of 950 feet from west to east in a 

 second of time, and will imagine a tower sufficiently ele- 

 vated above its surface, the lop of which, must describe 

 a circle as much greater than the surface of the earth as 

 will require in the revolution round the axis, a circulatoiy 

 momentum of 1000 feet in the second to preserve its rela- 

 tive situation. Suppose a body to be projected from the earth 

 at the foot, exactly towards the top of the tower. At start- 

 ing, it possesses a lateral force of 950 feet in the second, 

 and during a second, has arrived at the sameheightas this 

 supposed point. Now where will it be ? The answer is 

 self-evident, it will be 50 feet behind the object towards 

 which it was directl)^ pointed atthe moment of itsdeparture. 

 It still retains its side force of 950 feet in a second, and on 

 returning to the earth atthe expiration of the second second 

 will reach the point from whence it started, although that 



