[44] The secrecy of the early writers of Italy on gunnery and kindred subjects has been remarked on by Maurice Cockle in his _Bibliography of Military Books_. He attributes it to two motives: fear that the Infidel (the Turk) might profit by the knowledge otherwise gained, and a desire to keep the secrets of the craft in the hands of their countrymen, whose knowledge and assistance the foreigner would then be forced to purchase. [45] _The Great Cannon of Muhammad II_: Brig.-Gen. J. H. Lefroy, R.A., F.R.S. Vol. VI of Proc. R.A.I. [46] Ascribing the deliverance of Constantinople from the Saracens in the two sieges of A.D. 668 and 716 to the novelty, the terrors, and the real efficacy of Greek fire, Gibbon says: “The important secret of compounding and directing this artificial flame was imparted by Callinicus, a native of Heliopolis in Syria, who deserted from the service of the caliph to that of the emperor. The skill of a chemist and engineer was equivalent to the succour of fleets and armies.” For the story of the manner in which its mystery was guarded at Constantinople, of its theft by the Infidel, and of the use he made of it against the Christian chivalry at the crusades, see Chapter LII of _The Decline and Fall of the Roman Empire_. [47] Grose: _Military Antiquities_. [48] Hayley’s MSS.: quoted by M. A. Lower. [49] Oppenheim. [50] Oppenheim. [51] Corned powder was graded in France in the year 1540 into three sizes by means of sieves which varied with the types of guns for which they were intended (see Hime: _Origin of Artillery_). By the end of the century the manufacture had evidently improved in this country. “Some do make excellent good corn powder, so fine, that the corns thereof are like thime seed,” wrote Thos. Smith in his _Art of Gunnery_, A.D. 1600. [52] Oppenheim. [53] Bourne: _The Art of Shooting in Great Ordnance_, 1587. [54] Sir J. K. Laughton: _Armada Papers, N.R.S._ [55] Smith demolished, to his own satisfaction, a theory current that some molecular movement of the metal took place at the moment of gunfire. “I asked the opinion of a soldier, who for a trespass committed was enjoined to ride the canon, who confidently affirmed, he could perceive no quivering of the metal of the piece, but that the air which issued out of the mouth and touch-hole of the piece did somewhat astonish and shake him.” [56] The advantages of large calibres had been appreciated in the previous century. Sir Richard Hawkins, in his _Observations_, printed in 1593, compares the armament of his own ships with that of his Spanish opponents, and says: “Although their artillery were larger, weightier, and many more than ours, and in truth did pierce with greater violence; yet ours being of greater bore, and carrying a weightier and greater shot, was of more importance and of better effect for sinking and spoiling.” [57] Oppenheim.