Major J. G. Barnard on Elongated Projectiles. 193 
the escaping currents, their whole force is expended in destroy- 
ing velocity and generating pressure. On the anterior quadrant 
mn the resultant of the forces p, p', &c., is from n towards m, an 
tends, almost entirely, to deflect the ball in that direction. 
Ou the quadrant 7 the resultant of the forces p, p’, is parallel 
to the motion of translation, and co-incident in direction with the 
escaping current whose motion it accelerates and whose pressure 
it diminishes. Thus, taking the four quadrants, in one, op, the 
orces of friction are absent; in two, mp and no, they are ex- 
pended in producing an inequality of pressure on the two sides of 
the ball, tending to deflect the ball towards the side D (right); 
while in the anterior quadrant mn, they act to deflect the ball in 
the opposite direction F (left). 
It would have been difficult to decide @ prior’, which of these 
forces would prevail, though, while the force of friction is nuga- 
tory in one quadrant, in two (mp and on) it expends itself in 
developing forces tending to deflect to the right, and in only 
one, mn, does its direct action tend to deflect to the left; yet it 
_ Must be remarked that in this quadrant the air is most dense, 
friction the greatest, and that it acts directly upon the projectile. 
In the two lateral quadrants the air is less dense, and it is 
only through pressures developed in the air that it produces its 
ty a loss of effect ensuing in the medium through which it 
_ Experience has shown, however, that the forces developed in 
the two lateral quadrants prevail, and the projectile is deflected 
to the ri ht; and the experiments of Dr. Magnus give the same 
result when, instead of a projectile moving through the air, a 
current of air is directed upon a revolving cylinder. 
The deviation. of elongated projectiles, having rotary motion 
about their axis of figure, though many authors, Thiroux, Panét, 
“eg &c., have attempted to refer it to the same causes 
Ich produce the deviation in spherical balls, is evidently gov- 
Y other causes. : : 
iy only do such writers have to make, as to the direction 
the axis maintains, assumptions which conflict with each 
urse the division into quadrants which I have made is arbitrary, and only 
simple means of illustrating how the conflicting effects are uced from 
_ and the same cause, comprehend under the term friction, al) the forces by 
+ mechan: ical collision of particles; and this is the usual meaning of the word in 
ection, Poisson has considered friction only in its direct action, i. e., 
of the forces p.p’, &e., of Fig. 8, and, deducing therefrom a secs ce ea 
‘ late the di 2 4 
beside, _ Nevertheless it is all we ean account for, and the experiments of Mag- 
te to indicate its ade ‘ 
S, Vou XXIX, No, 85.—MARCH, 1660. 
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