Nearly every kind of gun is made at Woolwich, from the light field-piece to the guns which form a siege-train. Every gun, after being cast, undergoes a proof process, the strength of heavy ordnance being tested by the fire proof. The guns being laid on the ground in front of a target, or butt, with their muzzles towards it, slightly elevated, they are loaded with the regulation proof charges, and fired by means of a galvanic battery, which is placed in a bomb-proof building, and the current of electricity conveyed to the tubes in the guns through copper wires. Each gun is then searched by a long rod having a number of steel springs at the end, each of which has a spike attached; these springs are released from a grasping ring when at the bottom of the barrel, in the same manner as a cork-drawer. Any flaw in the barrel is at once disturbed in passing the searcher up and down. The soundness of the metal itself is tested by what is called the water proof: a hollow, wooden plug, covered with leather, is fixed in the muzzle of the gun by chains, which pass round the trunnions and are connected with the main pipe of the waterworks. A pressure of about 50 pounds weight to the square inch is thus obtained, and water is forced into the gun barrel until it issues a continuous stream from the vent (touch-hole). A wooden plug is then inserted into the latter, and a few more strokes given by the engine. If any water has penetrated through the thinnest part (the neck), the metal is unsound. The next, and last, test is the sun proof. After two or three days, the bore, being supposed to be perfectly dry, is examined by reflecting the sun's rays into it by means of a mirror, and if any part appears wet, it indicates a flaw. The sighting process is the last operation. In the construction of carriages, wheels, etc, many men are constantly employed. The timber used is principally ash, elm, and oak; it is crosscut and planed, and all the holes for rivets, bolts, etc, are bored by machinery; but the various parts of the carriages are finished and put together by hand.