The structure of the onager has excited unusual dif ficulty among antiquarians, chiefly owing to the discor dant words of cotemporary writers. Ammianus Mar cellinus, we have already seen, considered it and the scorpion as the same. Scorpio, lie continues, autem quoniam aculeum desuper babet erectum, cui than: onagn vocabulunz indidit cetas novella, ea re, quod asiniftri cum venatibus aguntur ; ila minus lapides, post terga calci trando emittunt, ut pectora sequentium, acct pczfractis ossibus capita ipsa displodant. At all events, it is universally agreed that the onager was a machine equally powerful and destructive. But on comparing the different descriptions of the ancients and their com mentators among the moderns, the power of the onager seems to have had a perpendicular motion, and to have produced the combined effect of a sling and balista. A long lever was inserted at right angles to a bundle of cords horizontally stretched, and in the centre of them. If the tension was considerable, it is evident that it would be infinitely increased by raising the end of the lever so as to describe a circular arc in the air ; then bringing it down to a point opposite to that whence it was moved, a full semicircle was described, and the tension augmented to the highest degree, so that a strong power was required to retain it in that forced position. Let us suppose a machine in this state ; if a sling containing a stone be attached to the end of the lever, and by a trigger the restraining power removed, the lever having escaped, will, in the course of the half perpendicular revolution it performs, discharge the stone with violence from the sling. An onager was construc ted, according to this description, at the siege of Gib raltar. It was found more effectual than an implement of the catapulta kind, also constructed there, which could throw a six pound ball.
Long after the invention of gunpowder, similar ma chines were retained in the European armies. We read in our older chronicles, and in those of almost all other nations, concerning machines for projecting ponderous substances on contending armies, and particularly on the besiegers and besieged of fortified places. or these may be enumerated the trebuchet, which somewhat re sembled the onager in combining the sling and lever, for throwing great stones : the petrary and beagles or bibles, for the same purpose. The es/27-Mga/ discharged large stones ; the robinet and mate griffon, both darts and stones. The war wal,C was used in sieges in Britain : Matthew of Westminster relates, that Edward I. of England emplOyed this engine in 1303, at the siege of the castles of Stirling- and Brechin, during his invasion of Scotland. Sir Thomas Maule stood on the walls of the latter, wiping away the rubbish with his handker chief in derision of the besiegers, " until the engines swept both him and the walls away." The engine brought against Stirling castle discharged stones of two or three hundred weight. We are told that millstones could be projected, as also the dead bodies of men and putrid horses, their power was so great. There some doubt concerning the real construction of the war wolf, which we are unable to elucidate. The mangonel was likewise a projectile engine, used for throwing stone's; and it was sometimes adapted in such a manner as to discharge five or six at once. Its greatest range is reputed to have
been 1042 yards. We should remember, however, that the degree of elevation not being specified, or the other precautions taken in using the ancient machines, we are ignorant of the real distance to which their load could be projected. _ Such is a very brief description of some of the most noted offensive arms, employed in hostilities chiefly before the invention of gunpowder, which, with small and simple apparatus, produces the most wonderful and destructive consequences. But, previous to the disco very of this substance, there was another combustible well known, the preparation of which has since been lost. We allude to Greek fire, which is said to have been invented in the seventh century in the East, and to have been adopted by the Saracens and Arabians in their contests. Although the ingredients composing Greek fire are specified by authors, they were kept se cret by those who used it ; but there can be little doubt that it was pretty generally known ; and we learn that the Infidels successfully employed it against the Chris tians during the holy wars. We are not fully aware of the mode in which this combustible operated, or how it was turned to effect. It seems that it was vomited forth in great quantities from machines containing it. Both in battles and sieges it was employed under the name of wild fire, and was most probably the same sub stance which we have above remarked was affixed to the heads of arrows. Notwithstanding the secret of composing Greek fire is lost to the public, it is confi dently reported that some years ago a chemist of this country invented a similar combustible. But govern ment, unwilling to augment the miseries of war, with laudable discretion bestowed a pension on the inventor, which should he continued so long as the secret was retained. The like discovery is said to have been made both in France and Rolland, and suppressed by analo gous measures.
The antiquity of gunpowder is unknown. We are taught to believe it an invention of the thirteenth or fourteenth century ; but there are good grounds for as cribing it to a period much more remote. Possibly it came from the East : we can hardly suppose the expli cit terms used to denote it, setting aside those of Roger Bacon, can apply to any other substance. Some emi nent authors have judged the invention of this dreadful combustible as of real utility to mankind, not in aiding their hostile operations, but in lessening slaughter and destruction. They affirm, that it is more consonant with humanity that war should be conducted at a distance, where superiority soon becomes evident, than that troops should come to close encounter. They justly observe, that personal prowess has a smaller share in character ising a modern hero, and that when men engaged hand to hand of old, the victor could only assure 'himself of success by finding no more of his enemy to kill. Now, on the other hand, the very terror inspired by the for midable apparatus of a siege, the thunder of cannon, and preparations for assault, frequently determine the contest, before the combatants have had time to spill each other's blood.