8 
posed gun will require a twist of rifling so sharp as to give a large angle of opening 
to the shrapnel, thereby wasting most of the bullets. One of them works out the 
angle as 20° for medium ranges. 
General Wille replies that this calculation is founded on the formula in the Eng- 
lish text-book of gunnery. As however this formula gives results differing over 
30 per cent. from those practically obtained from the German field gun, he distrusts 
it and proceeds to work out a formula of his own: 
Tn: Ca Vi + 02 sin® a 
2 vo+s 
where 6=angle of opening, % the radial velocity due to the scattering action of 
burster, » the remaining velocity, a the angle of rifling, and s the forward velocity 
due to base burster. Hence, taking angle of rifling at 7° or 1 in 26, s and 4 
140 f.s., v 2110 and 1530 fis. respectively, 0=174 degrees at 1000 yards and 
233 degrees at 2000 yards. Or putting s==260f.s., v=2152 f.s., the angles 
become 16 and 20 degrees, 
Note—These results do not correspond with those obtained by our methods, 
General Wille, working Siacci, gets 1530 f.s. at 2000 yards. According to the text- 
book, taking a co-efficient of +9, this should be 1750f.s. Perhaps the Secretary 
will ask Professor Greenhill kindly to settle this point for us. 
Again, taking the twist (vide text-book) at lin 28, and the forward velocity 
due to burster at 100 f.s. only, we get by Nicholson and Hadcock’s formula an 
angle of opening of 11° 14’ at 2000 yards. This sounds much nearer the truth 
than General Wille’s result. 
(To be continued). 
