The mariners magazine, or, Sturmy's mathematical and practical arts containing the description and use of the scale of scales, it being a mathematical ruler, that resolves most mathematical conclusions, and likewise the making and use of the crostaff, quadrant, and the quadrat, nocturnals, and other most useful instruments for all artists and navigators : the art of navigation, resolved geometrically, instrumentally, and by calculation, and by that late excellent invention of logarithms, in the three principal kinds of sailing : with new tables of the longitude and latitude of the most eminent places ... : together with a discourse of the practick part of navigation ..., a new way of surveying land ..., the art of gauging all sorts of vessels ..., the art of dialling by a gnomical scale ... : whereunto is annexed, an abridgment of the penalties and forfeitures, by acts of parliaments appointed, relating to the customs and navigation : also a compendium of fortification, both geometrically and instrumentally / by Capt. Samuel Sturmy.

SECT. XLVI. A Piece of Ordnance at the same Elevation, and towards the self-same place, with the like quantity of Powder and Shot, discharged several times, what difference there is in their Ranges.

THere hath been a Piece discharged in the space of an Hour seaven times, with the like quantity of Powder, Shot, and Mounture, and their Ranges have been fonud as followeth; the first Shot was conveyed 418 Paces, the second 438, the third 442, the fourth 434, the fifth 427, the sixth 412, the seaventh 395; so that the greatest difference from the first Shot was 24 Paces; this every Gunner must take notice of, if he intends to Shoot well at Random; the reason of these things is this, the first Shot of Powder found, the Chamber of the Gun moist, and the Air quiet, the second Shot, the Chamber was dryed, and the Gun in a good temper, and the Air moved towards the Mark with the first Bullet, and having less assistance than the first, went beyond, and made the best Shot; and every Shot after, will come shorter and shorter, as the Gun grows hotter and hotter; the reason is, by how much hotter the Piece is, by so much the more attractive is the concavity of the Piece made; and because the Shot is driven forth or expelled with no other thing, than by the Air's exaltation, or Wind, caused through the Salt-Peter; and therefore the oftner the Piece is Fired, and the more heat, the more attractive, which suppleth and retaineth continually more of that Wind, which should serve to expel the Bullet; and therefore the virtue expulsive in that Piece, doth more and more decrease, and the Shot flyeth not with that swiftness, as it did before in the 2 first Shots, which dryed and brought the Gun into his best temper; but the third and fourth Shot is but little difference from the first, but the rest will differ every Shot.

Nicholas Tartaglia doth report, that many Shots being made at a Battery by a Piece, it chanced by some occasion, the Piece rose up in such sort that the Piece touched the ground with its Mouth; a little Dog running by, did smell into the Mouth of the Piece, and after a little time, was drawn almost to the further end of the conca∣vity: they pulled him out almost dead; this was done by the virtue Attractive.