396 NOTICES OF THE MEETINGS {March 3, 
in the motion of projectiles of an elongated form shot from rifled 
guns, and which consequently rotate about their axis, while passing 
through the air in the direction of that axis. 
He mentions the fact that artillery experiments in different coun- 
tries with rifled cannon and missiles of a cylindical form with a 
conical apex, always shew a deviation of the point of the missile to 
the right, the rifle-spiral being right-handed. 
To explain the nature of this deviation was the object of special 
experiments on the part of the Prussian Artillery Commission, in 
which Professor Magnus assisted. The missiles were fired with 
low charges, so as to allow the motion to be accurately observed, and 
it was found that the axis remained sensibly in the direction of the 
tangent to the curved path, while the deviation to the right was always 
clearly marked. He observes that left-handed rifles have never been 
tried. 
Professor Magnus, after some fruitless conjectures as to the cause, 
at length sought it in the principle of the composition of rotatory 
motion. He tried experimentally the effect of a current of air ona 
projectile of the form employed, by inserting such a body instead 
of the rotating sphere in Bonenberger’s apparatus, and observing 
the effect on it, first at rest, and then in rotation, when the strong 
current of a blowing machine was directed against the conical apex. 
When at vest, the current elevated the apex; owing to the form of 
the missile the resistance acting not through the centre of gravity, 
but above it: when in rotation no elevation took place, but a deviation 
in the direction of the axis, in a direction opposite to that of rotation. 
To shew the application of the principle in this case, he observes 
that the axis of the elongated projectile, which for an instant 
coincides with the tangent to its curved path, momentarily changes 
its direction, so that the front extremity or apex falls below its 
former position. Or, for a single instant it may be regarded as 
if locally at rest, but turning about its centre of gravity so as to 
depress the apex. 
If the motion were simply in the direction of the axis, the re- 
sistance of the air would operate directly against it; but when the 
apex is continually tending to turn downwards from that line, the 
resistance acts against it partially upwards, and thus tends to raise 
the apex. 
Thus, at a given instant, the elongated projectile may be re- 
presented by the rotating part of the apparatus just described. 
When there is xo rotation, the resistance of the air tending to 
raise the apex is represented by the weight at the lower end, which 
produces the same effect. 
When a rapid rotation is communicated, (suppose from left to 
right of the gunner,) the result will be, zo elevation of the apes, 
but a dateral movement, or commencement of a rotation round the 
vertical,—in astronomical language retrograde, if the former rotation 
be direct ;—but which beginning from the opposite part of the circle 
is, relative to the operator, towards the right. 
