CAUSES OF DRIFT. 223 
If Fig. 1 represent the pointed projectile of the gyroscope, it will be 
found that a pressure of a pencil or pen, or of a blast of air exerted 
anywhere between a or 0, will as before explained raise the point when 
the projectile is not rotating; but if the pressure or blast of air be 
directed in like manner when it is given a rapid right-handed rotation, 
the point will move slowly to the right (see Fig. 5, representing a front 
view of the shot). Then as, by the point moving towards the right, 
the force will gradually act on the left of the projectile, its point 
will gradually droop ; as this motion proceeds, the force will come to 
act above the point, which will cause it to move to the left and 
finally acting on the right the point will rise. In fact, as long as the 
rapid rotation and the pressure continues the point will describe a slow 
circular motion* (0b. b0., Fig. 6.) 
Let us now examine the effect produced on a flat-headed projectile ; 
and for this purpose, the flat base, instead of the pointed head of the shot 
of the gyroscope, must be subjected to pressure by touch or blast. When 
such pressure is exerted below the central point, the flat end (or head) 
will not rise as with the pointed head, but will as before explained 
droop (see Fig. 2). If now the projectile be given a rapid right-handed 
rotation, as with the pointed shot, the pressure will be found to cause 
the flat head to move to the left instead of to the right, the consequence 
being that the slow circular motion of the head proceeds in the opposite 
direction. 
To apply these observations practically. If a pointed projectile 
having a right-handed rotation, be fired with a high velocity, the 
resultant of the air’s resistance, which would tend to raise the point if 
the projectile be not rotating, will, it must be evident from what can 
be observed with the gyroscope, give the point a lateral movement to 
the right. As this lateral movement of the point proceeds, so will the 
resultant act more and more to the left of the vertical plane, passing 
through the longer axis of the projectile, and therefore, as with the 
blast or the pressure acting on the gyroscope, the point will soon begin 
to droop. In fact, there is very little doubt but that the longer axis of 
an elongated shot does not remain parallel to its primary direction, 
when the velocity is high enough to create considerable resistance; but 
the point of the shot will first move to the right, then downwards, still 
keeping to the right, then to the left, and so on, describing a portion of 
the circle, the continuance of the motion depending upon the time of 
flight and the velocity maintained. As the velocity becomes low the 
* For a more detailed account of such experiments with the gyroscope, and an explana- 
tion of the cause of this circular motion of the point, see “Modern Artillery,” 2nd 
edition, page 251. In the “Text Book,” the movements of the shot of the 
gyroscope are caused by attaching weight to the suspending rings ; but this is not so 
satisfactory or intelligible as the employment of a strong blast, which I used for 
years at the R.M. Academy, 
