AND ON A PH.ENOMENON OP ROTATING BODIES. 221 



the direction of the deviation in left-handed rifles : but the con- 

 stant deviation to the right in right-handed, leaves no room 

 for doubt, that the direction of this deviation is conditioned by 

 the condition of the rifle ; and that in left-handed also, a con- 

 stant deviation, but to the left, would occur. 



It were certainly desirable, however, to have this confirmed by 

 actual experiment. 



By firing such elongated projectiles at a target, it has been 

 found that the axis of the projectile coincides nearly with the 

 tangent of the trajectory. If the axis and tangent continually 

 and exactly coincided, the resistance of the air, whose direction 

 coincides always with that of the tangent, would act always 

 parallel to the axis. The motion of the air all around the axis 

 would then be the same, and hence resistance could produce no 

 lateral deviation. But the experiments, shortly to be described, 

 show that the axis is not exactly tangential to the trajectory, 

 but, on the contrary, makes always a small angle with it ; and 

 hence, also, at this angle the resistance of the air must meet 

 the projectile. 



It might at first be thought that this small angle was suffi- 

 cient to produce a decrease of pressure on the one side, and in- 

 crease on the other, as in spherical projectiles ; but a closer 

 examination shows that if this were the case with a right-rotating 

 projectile, there would be a decrease of pressure on the left side 

 of the above-mentioned observer, and consequently a deviation of 

 the whole projectile towards this side ; whereas we have seen that 

 it is ever deflected towards the opposite side, i. e, to the right. 



The cause of the deviation in question, that is, of elongated 

 projectiles, cannot therefore be the same as that of spherical 

 ones. '^^^ f^iuRn wM «:jjjtji mui 



To discover this cause, it appeared first necessary to observe' 

 more closely the direction of the projectile's axis during its 

 motion. ^ -^ ^^' 



The members of the Royal Artillery Commission, entrusted 

 with the execution of the Commission's experiments, have 

 obligingly made several for the above purpose. Such elongated 

 projectiles were discharged with so small a charge of powder, 

 that it was possible for the eye to follow their motion, and to 

 observe the position of the axis during the motion. In these 



