28 



[March 13, 



I found that a homogeneous solid disk, formed slightly oval below, 

 Would strike as fired (in a vertical plane) when the centre of gravity 

 was "above." 



There are three ways in which, as I have found, disks may pass 

 through the air (as seen by the target, and shown in figs. 9, 10, 11). 



1st. Concentricity, or EC- Fig. 9. 



centricity, but with centre of 

 gravity not "above," causes a 

 disk to strike in any irregular 

 position (fig. 9). 



2ndly. When the centre of 

 gravity is "above," but there 

 is something within the bore 

 to hamper but not arrest the 

 rotation of the disk in the bore, such as too thick a sabot, or great 

 fouling and insufficient wind- Fig. 10. 



age, the disk strikes with the 

 edge, but not upright as fired 

 (fig. 10). 



3rdly. Centre of gravity 

 "above," Vith the attending 

 conditions which have been 

 before mentioned, gives a re- 

 sult as previously described 

 and shown in fig. 1 1 . 



The difficulty of destroying 

 "sabots" is much greater in 

 models than large guns. 



The penetration of disks when 

 striking with the edge is great ; 

 with a 2-oz. charge, at twenty- 

 five yards, the penetration has 

 commonly been through three 

 4-inch planks of elm ; and with 

 half an ounce more powder and a wronght-iron disk, through three 

 6-inch beams of elm, the latter with the grain of the plank parallel 

 to the plane of the disk, the former with it usually transverse. The 

 difference of direction in grain of wood causes in such experiments 

 about 2 inches difference in penetration. 



Fig. 11. 



