228 MAGNUS ON THE DEVIATION OF PROJECTILES, 



its axis being equally inclined to the horizontal direction of the 

 current, the axis assumed always a horizontal position. That 

 part of the cylinder, therefore, facing the approaching current, 

 was depressed, whereas in the pointed body this part was ele- 

 vated ; from which we may conclude that the elevation of the 

 latter is due to its pointed form. 



The pointed body was next exposed to the action of the hori- 

 zontal current while rotating within its ring. If, as before, the 

 axis was in the vertical plane through the middle of the current, 

 and its apex somewhat above the horizontal plane through the 

 centre of gravity, the latter moved slowly sidewards, at first in an 

 almost horizontal direction ; soon, however, its direction became 

 inclined. When the body rotated to the right, the lateral 

 motion of the apex was towards the right; and when it rotated 

 to the left, the lateral motion was also to the left. If the rota- 

 tion continued until the apex sank below the horizontal plane, 

 then its lateral motion again gradually decreased. It moved, 

 therefore, exactly as was above predicted when the resultant of 

 pressure passed through the part of the axis above the centre 

 of gravity, i. e, the part situated between the centre of gravity 

 and the apex. 



From these experiments, we may conclude that the deviation 

 of elongated projectiles is caused by the resistance of the air 

 seeking to elevate the apex. The elevation hereby produced is, 

 however, scarcely perceptible, for during rotation the forces 

 acting on the mass of the projectile so combine themselves, that 

 the apex, instead of being elevated, is moved sideways, and 

 indeed, towards the right when the projectile rotates to the 

 right. In consequence of this motion to the right, the re- 

 sistance of the air presses the projectile's centre of gravity 

 towards the same side, and thus produces the deviation. At 

 the same time the apex sinks, and thus it appears as if the 

 pressure of the air against the hinder part of the projectile was 

 greater than that against the fore part, whereas, in fact, this 

 pressure is greatest on that part of the axis which is placed 

 between the centre of gravity and the apex. 



I believe the cause of the deviation of elongated projectiles 

 is thus fully explained, and with it that of the whole phaeno- 

 mena of deviation, as well of spherical as of elongated projectiles. 



