. 214.

THEORY AND TRACTICE

TRACT 37.

plane. From which it is hoped that some aid may be de-rived towards ascertaining the resistance of the medium, andits effects on other elevations, 8cc, and so afford some meansof obtaining easy rules for the cases of practical gunnery.

Penetrationsolid /

Powder 2

s of Ballm woo

4 , ~

Us intod.

8 07 ,

7

16-6

13-5

18-9

21-2

18-1

20-8

20-5

Means 7

15

20

9. Another subject of en-quiry in the foregoing experi-ments, was, how far the bailswould penetrate into solidblocks of elm wood, fired inthe direction of the fibres.

The annexed tablet shows theresults of a few of the trialsthat were made with the gunn° 2, with the most frequent

charges of 2, 4, and 8 ounces of powder; and the mediumsof the penetrations, as placed in the last line, are found tobe 7, 15, and 20 inches, with those charges. These pene-trations are nearly as the numbers

2, 4, 6, or 1, 2, 3 ; but the charges of powder are as

2, 4, 8, or 1, 2, 4; so that the penetrations are propor-tional to the charges as far as to 4 ounces, but in a less ratioat 8 ounces; whereas, by the theory of penetrations, thedepths ought to be proportional to the charges throughout,or, which is the same thing, as the squares of the velocities.So that it seems the resisting force of the wood is not uni-formly or constantly the same, but that it increases a littlewith the increased velocity of the ball. This may probably beoccasioned by the greater quantity of fibres driven beforethe ball; which may thus increase the spring and resistanceof the wood, and prevent the ball from penetrating so deepas it otherwise might do.

10. From a general inspection of this second course ofthese experiments it appears, that all the deductions and ob-servations made on the former course, are here corroborated

and strengthened, respecting the velocities and weights of theballs, and charges of powder, &c. It further appears also,