The arte of gunnerie. Wherein is set foorth a number of seruiceable secrets, and practical conclusions, belonging to the art of gunnerie, by arithmeticke skill to be accomplished: both pretie, pleasant, and profitable for all such as are professors of the same facultie. / Compiled by Thomas Smith of Barwicke vpon Tweed souldier.

How any Gunner or gunfounder may by Arethmiticke skill, know whether the trunions of the peece be placed rightly on the peece or not.

Measure the length of the bore of the peece, from the mouth to the breech, deuide that measure by 7, and multiply the summe that commeth in the quotient by 3, the product will shew you how many inches or other measure the trunions ought to stand from the end of the lowest part of the concauity of the sayd peece at the breech.

And note that the trunions ought so to be placed, as ⅔ parts of the circumference of the peece may be seene in that place whereas the trunions are set.

Example.

Admit the cilinder or concaue of a Cannon, or o∣ther peece of Ordinance be 10 foote ½ long, I demaund where the trunions of the sayd peece ought to stand?

Answere.

Reduce the length of the concaue of the peece into inches, you haue 126 inches, the which deuided by 7, the quotient is 18, that multiplied by 3, makes 54 in∣ches, or 4 foote ½, so farre ought the trunions to be pla∣ced from the breech or lowest part of the hollow conca∣uity of the sayd peece.

Another way.

Or multiplying the length of the concaue of the peece by three, and deuiding the product by 7, the quo∣tient will shew the true place, how farre the trunions

ought to stand from the lowest part of the bore or con∣cauity of the peece.

Example.

126 inches the length of the concaue of the peece, multiplied by 3, makes 378 inches, which number de∣uided by 7, the quotient is 54 inches as before.

And note that the trunions of euery peece were in∣uented to hold the peece vp in her cariage, to moue her vp and downe to make a perfect shot, and to hold her fast in her cariage, after she is discharged: for if the tru∣nions be placed too neare the mouth, the peece will be too heauy towards the breech, so as the Gunner appoin∣ted to serue with her, shall haue much adoe to raise her, to coyne her vp or downe, or being placed too neare the breech, the contrary will happen.