OF GUN-METAL.

*•

IT 7

appears the necessity of having gun-metal so hard as not toadmit of any cavity being formed by the action of the elasticfluid, which is more violent in proportion, as the chargeoccupies a greater length of the bore: wherefore, thoughcannon powder is less inflammable than war powder, (Tieatdeon Powder) and consequently generates less elastic fluid inequal times; yet, in the guns formed of the common mix-ture, and fired with 26; Ib. of cannon powder, the lessquantity of fluid having a longer space to pass through, ac-quired greater velocity ; so that notwithstanding the superiorhardness of the metal, the cavity was of the fame depth as inthe guns cast from R and charged with i6§ Ib. of war powder.

40. To confirm the result of the foregoing experiments,a 32 pr. cast from the common mixture was, in August1759, fired twice with each of the following charges of sa-luting powder, which was the strongest then at hand; fivestrokes were given by two gunners to the wad over the pow-der, and three to that over the shot: the piece was laid atthe elevation of 22s 0 .

Experiments in 1759.

Weight of Powder.

9 4

13 2

16 6.

Length of Range,

Yards.

3968

4456

4659

After 'the two first rounds, the gun was examined, but;no cavity discovered; after the two rounds with the 13Ib.2 oz. an orbicular caviry was formed, whose greatest depthwas Aj. of an inch, at the position of the wad between thepowder and shot; and after the two rounds with the 16 Ib.6 oz. the cavity was much enlarged, its greatest depth wastt of an inch at the place where th^ wad was lodged atthe last discharge.

41. Some rounds were fired in September 1759, from an8, 16, and 32 pr. cast of a metal similar to D, M, (29) ;in order to determine the proper degree of hardness forpreventing the formation of orbicular cavities, even withextraordinary charges. The charge was of saluting powder,equal to f of the weight of the shot; the guns were laid at15% and the wads rammed as before; after the experiment,W 3 nos