The date of this work is a subject of controversy; some writers place it as early as the eighth century, and it can only be said with certainty that it is not later than 1280. The latter date is fixed by the death of Albertus Magnus, who, in his book “De miribilibus mundi,” from internal evidence, is obviously plagiarising the Liber Ignium. Friar Roger Bacon (1214–94), in two of his works, refers at least twice to compositions containing saltpetre, powdered charcoal, and sulphur. In one place he refers to fires that “shall burn at what distance we please”; in another to “thunder and corruscations,” which references seem to suggest that he is describing something of a pyrotechnic nature rather than the simple effect of gunpowder. His description in no way indicates that he claimed to be the inventor, but rather as something well known before. Dr. Jebb, in his preface to Bacon’s “Opus Majus,” refers to what seems to be an early example of both the rocket and the cracker. Dutens, in his “Inquiries into the Origin of the discoveries attributed to the Moderns” (1790), makes reference to many early writers, which are mostly so vague and exaggerated that no definite conclusion can be drawn from them; most refer to the early uses of Greek-fire or similar composition. Don Pedro, Bishop of Leon, says that “in 1343, in a sea combat between the King of Tunis and the Moorish King of Seville ... those of Tunis had certain iron tubes or barrels wherewith they threw thunderbolts of fire.” This description, if accurate, may be thought to suggest the use of cannons, but it is more likely to refer to the use of Greek-fire; this composition will, in certain proportions, if charged into a strong tube, give intermittent bursts, projecting blazing masses of the mixture to a considerable distance. The writer has seen this effect produced in a steel mortar of 5½ inches diameter, the masses of composition being thrown a distance of upwards of a hundred yards, a considerable range in the days of close warfare. Anyone who has seen this phenomenon will at once realise that here probably is the true solution of many obscure early references to explain which so much ingenuity has been expended. An interesting fact which seems to have escaped the notice of writers on this subject is that Theresa, daughter of Alfonso V. King of Leon and the Asturias (A.D. 999), when married to Abdallah, King of Toledo, took for device on her coat of arms a mortar in which a powder is being pounded. This powder is supposed to represent gunpowder, a supposition which is supported by the motto, “Minima maxima fecit” (A little makes much). If gunpowder is intended, this must be one of the earliest references to its quality of exploding, and it is difficult to explain the meaning otherwise.