318 MESSRS. R. H. FOWLER, E. G. GALLOP, C. N. H. LOCK AND H. W. RICHMOND : 
Table IV. (continued). 
Gun rifled one turn in 30 diameters of the bore. 
All groups were stable. 
Group. 
Muzzle 
velocity, 
f.s. 
Group. 
Muzzle 
velocity, 
f.s. 
Group. 
Muzzle 
velocity, 
f.s. 
T yp 
e I. 
I. 22-24 
1119 
I. 25,26 
i 
1326 
1 
I. 27,28 
V 
1563 
Type II. 
II. 17-19 
1119 
II. 24 
1292 
II. 22,23 
1589 
Type III. 
III. 17-19 
1119 
III. 20, 21 
1292 
III. 22,23 
! ’ 
1567 
Type IY. 
IV. 21-23 
IV. 13-15 
900 
1078 
IV. 16-18 
IV. 19, 20* 
1547 
1547 
IV. 24-26 
2121 
the centre of gravity of the shell was moving normally to the card, f Thus the 
angle actually recorded by the shape of the hole in the card is the true yaw of the 
* Fired with cards on the far screens only, to determine by comparison the effect of the impacts on the 
cards. 
t The angular motion of the axis of the shell is comparatively so slow that it can be ignored during the 
interval in which the shell is passing through a card. For instance, with the shells used in this trial the 
change in c j>, the orientation of the yaw, is never as much as 3| degrees during the complete passage 
through the card, and the change in S never as much as 8 minutes. These quantities are of the same 
order as the errors of observation and may be ignored. Thus the shell can correctly be regarded as 
equivalent for cutting purposes to its circumscribing cylinder (of indefinite length) whose generators are 
parallel to the direction of motion of the centre of gravity. 
If the direction of motion is normal to the plane of the card at the moment of impact, a certain hole 
will be cut in the card, whose shape will be precisely that of the normal cross-section of this circumscribing 
cylinder. But if tbe card is tilted through a small angle t about any axis in its own plane, the hole 
made by the shell will be the same as the cross-section of the supposed cylinder by the plane of the card 
