356 MESSRS. R. H. FOWLER, E. G. GALLOP, C. N. H. LOCK AND H. W. RICHMOND : 
y to be small and positive,* which does not fit in with the observations. Farther 
experiments would be needed to throw light on all these points. 
Path described, relative to the centre of gravity, by a point on the axis of the shell in front of the 
centre of gravity, shown on an enlarged scale. 
The total time taken from O to K is 0‘3647 second. On the scale used, 2 cm. distance from 0 
represents 1° yaw (very nearly), and corresponds to a linear displacement of 0 - 128 inch for the nose 
of the shell from the line of motion of the centre of gravity. 
In the fourth column what appears to he the most probable value of h is given; 
the values of f a in 'fable II. are based on these figures and obtained by the equation 
(see §§ 3.5 and 1.12) 
/h — 
hB 
pvr 4 
* The coefficient y comes from the swerving couple J (§1.12). This couple will only ai’ise if the 
swerving force K does not act through the centre of gravity. Since the air pressures are greater near the 
nose than near the base, we may expect K to act in front of the centre of gravity. By analogy with the 
connection between the direction of rotation and the direction of the resulting swerve on a golf or tennis 
ball at low velocities, we may expect K to act along the axis of M reversed in fig. 9, for a right-handed 
twist of rifling. This would result in a positive value for y. 
