PROCEKDINGS OF THE POLYTECHNIC ASSOCIATIOK. 57t 



power upon the progressive motion, the result will be, that pro- 

 jectiles shot from smooth bore pieces will describe circles, instead 

 of straight lines. Whenever the axis of rotation of the ball is 

 horizontal and at right angles to its progressive course, it will 

 strike under the mark, if the rotation in its front is in a down- 

 ward direction ; but if upward it will strike above the mark. If 

 the rotation is around a vertical axis from left to right, it will 

 strike to the left of the mark, and if from, right to left, it will 

 strike on the right side of the mark. 



I believe, it is laid down, that if a ball or globe could be placed 

 without the influence of any resisting or attracting medium, that 

 its centrifugal force would be equal on all its sides. But, if it 

 has a projectile motion in addition, this force may vary on differ- 

 ent sides. When it revolves around a horizontal axis at right 

 angles to the direction of the progressive motion, and downwards, 

 the matter of the ball in front, is carried down more or less, in 

 its rear, upward, underneath, in a contrary direction, and on top 

 in the same direction, more or less to its progressive course. 

 Now, it would seem, that as the momentum of the rotatory mo- 

 tion in one half of the bullet or planet, is, more or less, in the 

 direction of the progressive motion, and the contrary way in the 

 other half, might it not have a leverage and cause a deflection 

 from a right line direction ? As two forces from difierent direc- 

 tions will propel a ball in their averaged direction, why will not 

 the projectile and rotatory forces unite in an averaged direction ? 

 The tendency of a balance wheel to revolve after the impulse is 

 withdrawn, and of a globe hung by moveable gudgeons upon the 

 periphery of a large wheel, to revolve in the same direction with 

 the progressive course, seems to be some evidence that the rota- 

 tory force has a leverage upon the projectile force. 



May not then the aberrations given to projectiles fired from 

 smooth bore pieces be owing more to their globular shape, by 

 which they get a rotary motion, and that by using long cylindri- 

 cal ones, pointed and hollowed out at the other end may not sharp 

 shooting be attained with the progressive motion only. But if a 

 rotatory motion around an axis pointing to the mark, is ab- 

 solutely necessary, may not a spirally shaped chamber, behind 

 the ball, give such motion, and thus avoid the great expense of 

 rifling. 



Though some of the conditions in which the planets exist, may 

 be difi'erent from that of our projectiles, yet I do not see but that 



[Am. Inst.1 KK 



