PROOF CHARGES.
The Brass Mortars, and Howitzers are fired twice with their chambers full of powder, and an iron shell. The Mortars on their own beds at an elevation of about 75 degrees, and the Howitzers on their carriages at an elevation of about 12 degrees. The Iron Mortars are proved with a charge equal to the full chamber, and a solid shot equal in diameter to the shell. Royal or Coehorn Mortars, and also 24, and 12 pounders, or Royal Howitzers, having a hole of ·1 of an inch in depth in the chamber, or ·15 of an inch in the chase are rejected. A hole ·15 of an inch in depth in the chamber, or ·2 of an inch in the chase is sufficient to condemn the 10 and 8 inch Howitzers.
CARRONADES.
The bores, and chambers of Carronades must not deviate more than ·05 of an inch from their true dimensions, and positions.
PROOF CHARGES.
They are proved with two rounds, with their chambers full of powder, and one shot and wad. A hole of ·2 of an inch in depth in the bore, or ·1 in the chamber condemns the piece.
WATER PROOF.
All Ordnance, after having undergone the before-mentioned proofs, and the subsequent searchings, are subject to the Water proof. This is done by means of a forcing pump, having a pipe or hose fitted and secured to the mouth of the piece, and a plug to stop up the vent.
After two or three efforts to force the water through any honeycombs or flaws, which there may be in the bore, they are left to dry, and generally the next day examined by light reflected from a mirror. If the bore should contain any small holes or flaws, which have not been discovered by the former proofs, they are very readily found by this, as the water will continue to weep or run from the holes, after the solid parts of the bore are perfectly dry.
When a gun bursts in proving, the remainder in proof at the same time are subjected to another proof round.