1870.] on the ' Thunderer' Gun Explosion. 237 



and loading apparatus — for tlicy arc one and tbo same — is hydraulic, 

 and consists of an inclined cylinder so placed on supports as to 

 have its centre uj^on the jirolongation of an imaginary line passing 

 through the axis of the gun uhen in the loading position. Within 

 this cylinder is contained a plunger, which is hollow and has 

 within it a second plunger, so that the cylinder with its two 

 plungers may be likened to a threefold telescope. The inner plunger 

 carries on its end a head (the rammer), which is surrounded by the 

 sponge, not an actual sponge, but a sponge-like fabric ; the head is 

 hollow, and is supplied with water under pressure by being in con- 

 nection with a hole which extends along the centre of the plunger ; 

 the front of the head is provided with a little valve opening inwards 

 and kept closed, therefore, by the pressure of the water. There is a 

 small pin on the front of this valve, which projects. This being the 

 construction of the apparatus, the action is as follows. The man in 

 charge moves the lever, and thereby admits water under pressure into 

 the cylinder of the rammers, which water drives out the plungers, and 

 almost always, as it possesses the greater area, the large j^lunger starts 

 first and goes outwards (until checked by a stop), carrying with it the 

 smaller plunger and the head well up into the bore of the gun, and 

 then the smaller plunger starts out under the influence of the pressure, 

 and continues the carrying of the head forward until it reaches the 

 end of the bore, when the pin on the little valve strikes the rear end 

 of the bore, opens the valve, so as to allow the water to escape, to 

 wash out the gun and to saturate the sponge cloth. The lever is then 

 reversed, the water pressure is made to act upon certain annular 

 surfaces round about the plungers and in the reverse direction, and in 

 this way the telescope shuts up, withdrawing the head from the gun. 

 Two men then lift the cartridge and put it into the loading tube. The 

 projectile has been previously brought in a truck and placed on the 

 platform of the hydraulic lifting gear, and, the cartridge being in, the 

 lever is moved, which admits water pressure into a vertical hydraulic 

 cylinder, and thereby raises the plunger within it, carrying upwards 

 the platform, the truck, and the projectile to a definite position which 

 is one that places the projectile in the exact line of the bore. 



A papier-mache disc wad is next put upon the rammer head. You 

 will see the wad consists of a disc, of a tubular socket, and of a collar 

 round about that socket. The wad is held in place by the socket, 

 being received into a cavity provided for it in the rammer head, while 

 the collar keeps the back of the disc away from the head and from 

 pressing on the pin of the water valve, and thus prevents the pressure 

 exerted in ramming from opening that valve and deluging the gun 

 while loading. A wad is wanted for two reasons : one, the ordinary 

 one, that the ship may not in rolling cause the projectile to move in 

 the gun ; for this purpose wedge wads, of which I show you a sample, 

 have long been used. You will see that this wedge wad consists of a 

 large number of hard wooden wedges strung upon a rope, made up 

 into a ring just suited to go inside the bore, so that the wedges may 



