Writing in 1628, Robert Norton, in his book _The Gunner_, refers as follows to the early Tudor ordnance. “Gun-founders about 100 or 150 years past,” he says, “did use to cast ordnance more poor, weak, and much slenderer fortified than now, both here and in foreign parts: also the rather because saltpetre being either ill or not refined, their sulphur unclarified, their coals not of good wood, or else ill burnt, making therewith also their powder evilly receipted, slenderly wrought, and altogether uncorned, made it prove to be but weak (in respect of the corned powder used now-a-days), wherefore they also made their ordnance then accordingly (that is much weaker than now). For the powder now being double or treble more than it was in force of rarification and quickness, requireth likewise to encrease the metal twice or thrice more than before for each piece.” And, in fact, the weight of cannon increased in the period mentioned from eighty to two hundred times, the weight of culverins from a hundred to three hundred times, the weight of their shot. The slender large-bore built-up guns of the _Henry Grace à Dieu_ could only be used with a weak slow-burning powder. At the same time this slow-burning powder required, for its complete combustion, a great length of gun. These guns, such of them as were breech-loaders, must have suffered from the leakage of gas at the joints of their primitive chambers; in the case of the smaller pieces a serious inefficiency was the excessive windage allowed between shot and gun. Until the end of the sixteenth century the windage bore no direct relation to the diameter of the shot or bore of the gun: it was a fixed amount, one quarter of an inch. The effect, therefore, of the leakage of powder gases past the shot, the loss in efficiency of discharge, was greatest in the smallest guns.