16th. A vent-searcher, a steel wire of the length of the vent, bent to a right angle at the lower end and pointed. It is used for detecting imperfections in the sides of the vents.
17th. A semicircular protractor of metal for measuring the inclination of vents, or for ascertaining their deviation from the guide.
18th. A set of templates for verifying the shape of lock-lugs, the angle of the rear sight mass, the curve between the base-line and the front of rear sight mass, that at the end of the cascabel, the bevel of the breeching-hole, the opening of the cascabel, and the shape of the muzzle swell.
If the inspection should take place at the foundry, the templates used in chipping might be verified and used for inspection.
For guns of Dahlgren's pattern, a bronze model, showing the shape of the lugs and rear sight mass, and the position of the vents, is furnished as a guide to the contractors.
19th. A standard foot-rule for verifying measures.
20th. A foot-rule of steel for measuring the masses, the length of the trunnions, and for other purposes. The graduation should be extended to each end.
21st. A set of ring-gauges, large, medium, and small, for inspecting the projectiles used in proof.
22d. A small beam-calliper, with outside edges, for examining the adjusting rings and the ring-gauges.
23d. A platform balance, for weighing the projectiles used in proof, and for bringing the shells up to the standard weight. For use with the above there should be provided a bag of dry sand, a funnel, some wooden plugs for the fuze-holes, and a hammer.