CAUSES OF DRIFT. 225 
ment was, at the suggestion of Professor Magnus, made by a Royal 
Commission, appointed to carry on artillery experiments at Berlin.* 
A number of projectiles were fired with a charge, and consequent 
velocity so low that an observer could follow them with the eye, and 
even note with accuracy the position of their axes ; the following were 
the results obtained :— 
(1) All the observers stationed at intervals along the range unani- 
mously agreed, that the axis of the projectile during the whole time of 
flight remained nearly tangential to the trajectory, but nevertheless 
that, in the descending branch, it was easily seen that the point of the 
projectile was a little higher than could have been the case had the 
axis remained accurately tangential to the trajectory. 
(2) It was also admitted by all that, as much from the motion of 
the projectiles as from the furrows made in grazing the ground, in all the 
rounds fired, the point of the shot at the instant of touching the ground 
had a deviation to the right. (As shown in Fig. 8). 
It follows from the results of these direct observations that, during 
the motion of translation of an elongated projectile, the axis does not 
only not agree exactly with the tangent, but that it makes a certain 
angle with the vertical plane drawn through this tangent, and that the 
deviation thus arising from this is to the right. 
Many who are constantly employed in noticing the flight of shot 
assert most positively that when the velocity is not too 
high, they can clearly see the projectiles descend with Fig 8. 
their points downwards. It is difficult to say whether } 
this is a mere optical illusion, but the effects, on targets, / 
which can be examined at leisure, are more satisfactory | | aoe 
evidence then that of the mere view of a shot during [fA 
flight. Now it is almost invariably found that the holes 
made in targets are circular,even when elongated shot 
descend at considerable angles ; for instance, some 40-lb. 
shot fired at 7° and 10° of elevation, the angles of descent /[; 
for which would be about 9° and 13° respectively, cut | 
circular holes out of vertical targets made of thin wood 
covered with sheet lead. The most probable explanation 
of this fact must evidently be that the point of the shot 
had drooped during flight, so that, on striking, the 
longer axis was nearly perpendicular to the plane of the 
target. It would doubtless be most difficult to ascertain 
the exact position of the longer axis of a shot at any particular part of 
the trajectory, but this is hardly wanted ; for if at ranges generally 
required we can be pretty sure that the point will droop so as to allow 
the shot to strike nearly point first, there need be no fear but that the 
necessary practical results will be obtained. This drooping of the 
point is of importance, for did the axis remain parallel to its primary 
direction during flight, the projectile would, most probably, when fired 
at any but a very low angle, on striking an object of hard material and 
Solid structure, as a wall, iron plate, &c., turn up against it lengthways, 
and therefore produce but trifling effect. 
We will now take the case of a flat-headed projectile, which it was shown 
by the gyroscope turns to the /eft with a right-handed rotation instead 
| 
* Magnus, on the “ Deviation of Projectiles; and occasional papers of R.A. Institution, 
Vol. i., p 443. 
30 
