Pyrotechnia or, A discourse of artificiall fire-works in which the true grounds of that art are plainly and perspicuously laid downe: together with sundry such motions, both straight and circular, performed by the helpe of fire, as are not to be found in any other discourse of this kind, extant in any language. VVhereunto is annexed a short treatise of geometrie, contayning certaine definitions and problemes, for the mensuration of superficies and sollids, with tables for the square root to 25000, and the cubick root to 10000 latus, wherein all roots under those numbers are extracted onely by ocular inspection. VVritten by Iohn Babington gunner, and student in the mathematicks.

CHAP. LXV. The manner of making the aforesaid Engines for trying the strength of powder.

THE first is made in a circular form, with a neck comming from the circumference, which serves for a lid to the powder box, which box shall bee made to hold the quantity of a dram of powder, or there about, so that being covered with the lid, and fired, will blow, according to the strength of the powder, and moving, will turn about a circle of brasse, which is divided into certain equall parts, and so will shew the strength accor∣ding to the part it cutteth; for the greater the degree is that it is blown

[illustration] diagram of engines for determing the strength of powder

fig 20

up to, the stronger is the powder, and contrary. The form of this is re∣presented in the twentieth Figure, by the letter A.

• A representing the form of the whole Engin.
• B the powder box, which must be filled to the top.
• C the lid, which must be put on the sayd box, it being filled.
• D the circle of brasse to which the lid is fastned, which is divided into de∣grees, and runneth upon the pin E, passing thorow the center, with a screw to set it harder or easier.