272 VARIETIES OF SHOT-GUNS, ETC. 



and sliding in corresponding traverses, within the poste- 

 rior half of the breech-plug. These wings answer a treble 

 purpose firstly, they receive the pressure of the spring from 

 behind; secondly, they maintain a steady sliding action; and 

 thirdly, they are capable of receiving the pressure of the cam 

 (fig. 45), which is a double inclined plane fixed within the 

 plug, and which, when turned round, thrusts the whole 

 needle backwards. When this is done its posterior ex- 

 tremity being notched, drops upon the scear and is held 

 back after the cam is restored to its orignal position. In 

 addition to the notch for the scear (see fig. 43 c), there are 

 sometimes two others at the side (at d) for the reception of the 

 bolt, but in those lately made by Mr. Needham the stop is 

 effected by the bolt dropping into the scear instead of the 

 needle, as will be presently explained. The mainspring 



THE MAINSPRING. THE SCREW CAM. 



(HALF SIZE.) (HALF SIZE.) 



(fig. 44) is of very simple form, being merely a spiral spring 

 dropped into the posterior half of the plug and pressing 

 against the wings of the needle. Next comes the screw cam 

 (fig. 45), which is fixed within the plug, and is perforated by 

 a hole for the needle ; two inclined planes are so arranged 

 that as the plug is turned round they press upon the wings 

 in the needle already described, and push it back till it 

 catches the scear. As a matter of course these cams are 



reversed on the two sides 

 Fig. 46. of the gun, since the lever 

 in one case is turned to 

 the right and in the 

 other to the left. The 

 scear and spring, with the 

 trigger (fig. 46), complete 



SCEAR-SPRING, SCEAR, AND \j\ the actions in this lock, 



TRIGGER. (HALF SIZE.) t/ w ith the exception of the 



