116 
Proceedings of Royal Society of Edinburgh. [sess- 
On the Path of a Rotating Spherical Projectile. Part II. 
By Prof. Tait. 
[Abstract.) 
(Read January 6, 1896.) 
In addition to the authorities quoted in the first part of the paper, 
memoirs by Clerk-Maxwell and by Lord Rayleigh are referred to, 
also a passage in the Beibldtter zu den Ann. d. Physik. (1895, 
p. 289), which cites Helie, Traits de Balistique. 
The Author then considers the more obvious defects of the 
rudely approximate solution of the differential equations which 
is given in Part I., especially the omission of the direct gravita- 
tional effect on the speed, and shows how to take account of the 
effect of the observed gradual diminution of the angular velocity 
of the projectile. An improved solution of the problem of § 8 of 
the paper is also given. 
The Author stated that he had occasionally succeeded in obtaining 
the kink spoken of in Part I., the projectile being a humming-top 
made of very thin metal. He had also occasionally obtained a 
cusp, thus exhibiting the paradoxical result of a projectile’s path 
which is at no point concave downwards. 
i 
[Added Jan. 20th.) 
At this meeting the Author showed the kinked path to the 
Society in an exceedingly simple manner ; the projectile being 
a very large and thin shell of india-rubber which, contrary to 
his expectations, was found to preserve for a considerable 
time the spin given to it by cutting it sharply, in an 
obliquely downward direction, with the flat hand. The opera- 
tion is analogous to jerking in golf. This experiment can be 
successfully performed with great ease, and is a thoroughly 
illustrative one for the whole subject. 
