TRACT 31.

IN GUNNERY.

349

No.of thegun

Diameterof thetrunnion. 1 -

Diameter, Cehtre gravity or axis of

gun alone

Centre ofgravity ofthe wholebelowaxis

of thegun atcentre oftrunnions

be hi

muzzle

nd the

•entre of

trunnions

abovecent, oftrunnions

belowaxis ofvibration

1

2-2

7-00

18-5

1-4

1-24

89-06

80-47

2

2-2

5'89

24-5

1-S

1-24

89-06

80-47

3

2-25

5-06

37-4

4-2

1-11

89-19

80-50

4

2-2

4-84

51-3

3-0

1-02

89-28

80-44

The numbers in the last column of this table, are thevalues of the letter g, in the formula for the velocity bymeans of the recoil of the gun. This letter may always besupposed to have the value 80-47 inches, as the two lastnumbers of the column differ from it but '03 only, or aboutthe 2700 part of the whole, inducing an error of only abouthalf a foot in the velocity of the ball. The values of g, inthis last column of the table, were computed in the follow-ing manner.

188 G

917 E

Suppose the centres of gravity of thestem, gun, and leads, to be all reduced tothe line of the stem a t, connecting theaxis and centre of the trunnions t, in whichthey are situated very nearly ;so that g be the centre of grav. of the stem,c - -- -- - of the gun,

T ------ of the leads;

also the numbers on the right-hand side ofthese points, namely, 44‘25 and 89'06 and90-3, are the measured distances below theaxis at a; and the numbers on the left-handside, namely, 188, 290, and 439, are theweights of the bodies belonging to thosecentres of gravity. Then, from the property of the centreof gravity, we shall have these operations ;

290

729

439

- 44-25

- 80-47

89-06

89-81

90-30