THE EOYAL AETILLEEY INSTITUTION. 
73 
Plate 2. The gun with its fitments are here represented apart, 
(1) Shot leaded on the Prussian system. 
(2) Plate for refacing the block. 
(3) Steel or copper ring, of triangular section, about O'33 in. width towards the 
powder chamber, by 0*37 in. depth. The form of this ring is such that the gas 
exercises a wedge-like action within it, pressing the face of it against the circum¬ 
ference of the bore, and thus closing the junction of the block and gun. 
(4) The sliding stop for locking the block. 
(5) Aperture in the breech-block through which the charge is introduced and the 
gun sponged. 
This aperture in the most recent examples is lined with a sliding gun-metal 
tube ingeniously contrived to advance towards the bore of the gun as the block 
recedes from it, so that in the loading position when the face of the block is nearly 
half an inch clear of the front of the slot, the tube protrudes and touches it. The 
object is to prevent fouling being drawn into the open space, and the motion is 
effected by a couple of guide pins, one above and one below, which work in inclined 
grooves on the upper and under surface of the block. 
(6) Circular recess in the face of the block into which the steel or copper ring 
(3) is fitted when the block is in position for firing, this recess is in prolongation of 
the bore. 
(7, 8) Breech block shewing the grooves above and below by which it is guided, 
the handle for withdrawing it, the several stops, and the staple in which the locking 
screw (9) moves. 
(9) Screw with lever handles for setting the block home if required, and for 
starting it. The mode of action is best seen iu figs. 1 and 2, Plate l. 
