It is scarcely worth while to controvert such absurdities; the fable of perpetual lamps having faded before the dawning light of reason. Is it, however, to be credited, that the genius of Descartes did not secure him against this vulgar error? The views of that great man on the subject deserve to be quoted as a proof of the aberrations to which superior minds are subject. “After considering the fire produced by gunpowder,” says Descartes, “which is the most transitory in existence, let us inquire whether there can exist a flame, enduring without the aid of fresh matter for its support, like those found in the tombs of the ancients shut up for centuries. I will not vouch for the truth of their existence; but think it possible that in a vault so close that the air could never be disturbed, the parts of the oil transformed into smoke, and from smoke into soot, might, by sub-formation, arch themselves over the flame so as to protect it from the air, and render it so weak as to lose the power of consuming either oil or wick, so long as there should remain a shred unburnt by which means the primary element existent in the flame and identified with the little self-formed vault, might revolve therein like a little star. It necessarily follows that the second element became expelled on all sides, while trying to penetrate the pores still remaining in the little dome; and the flame which remained feeble while the place was closed, brightened the moment it was opened, and the external air admitted. The surrounding smoke dispersed, the flame recovers its vigour for a moment, and then expires. Such lamps, in fact, become perpetual, only from having exhausted their oil.”
This statement is extracted from the Fourth Book of the Principles of Philosophy of Descartes. In spite of the respect due to his name, we see in it only a tissue of verbosity exhibiting science at a nonplus, and advocating a groundless theory. But such a chimera on the part of so eminent a man, ought to afford consolation to second-rate capacities, as a proof that no one is exempt from delusions.
From Descartes, let us turn to Archimedes, who conferred ten-fold power upon the arm of man by arming it with the lever; and with becoming deference avow our want of faith in the mirror by the burning reflections of which he managed to destroy the Roman galleys!
“Combustible bodies,” observes Descartes, “cannot be ignited by means of mirrors unless comprehended in the necessary focus. Geometry shows us that the distance of a focus of a concave mirror is equal to the half of its sphere; that is, if the mirror have been set from a sphere of a radius of one foot, the distance of the focus will be of six inches. A sphere having a radius of one foot, gives, therefore, but a focus of six inches, so that to establish a focus at two hundred feet, would require a sphere with a radius of four hundred feet, or eight hundred in diameter! Besides, how could Archimedes procure such a mirror, when the art of casting mirrors was unknown, and the manufacture of glass in its infancy? That it was a metallic mirror is difficult to conceive. Such were the solutions attempted of an insoluble problem. Doubtful anecdotes are so often and so boldly adopted by the authors of antiquity, that we may regard as unsubstantiated all facts upon which they are silent. Neither Livy, Diodorus, nor Polybius mention the mirror of Archimedes; so that the invention is probably modern, and most likely a fable of the sixteenth century, prolific in inventions and amplifications. The press, then in its infancy, delighted in the propagation of marvels and fallacies attributed by their imbecile authors to the ancients, so as to assign them some semblance of truth. Among such inventions was the mirror of Archimedes.
Gallienus, indeed, mentions the burning of the fleet by Archimedes; but is mute on the subject of the mirror, which he could scarcely have omitted, had the fact been genuine. Tzetzes and Zoronas are the first who mention it; the former in the following words:
“When the Roman galleys were within arrow-shot, Archimedes caused an hexagonal mirror to be made, and other smaller ones, each having twenty-four angles, which were placed at a proportionate distance, and could be worked by their hinges and certain metallic blades; their position being such that the rays of the sun reflected upon their surface, produced a fire which destroyed the Roman galleys, though at the distance of a bow-shot.”
The author does not condescend to give his authority; relying for the evidence of his authenticity upon his confederate, Zoronas, who relates that, at the Siege of Constantinople, under the reign of Anastasius, Probus burnt the enemy’s fleet by means of brazen mirrors. He states that the invention was not new, but belonged to Archimedes, who, as testified by Dion, used them at the Siege of Syracuse by Marcellus.
The mutual confederacy of a couple of mountebanks is as easily understood as it would be susceptible of annihilation; did not such men as Kirchen and Buffon become sureties, not for what Archimedes has done, but for what he was capable of effecting. Previous to Descartes, the former had asserted the possibility of igniting combustible matter at a great distance by means of small plane mirrors, which could be managed so that the rays might be directed upon any given object. This was simply a theory; but Buffon decided upon making the experiment, the result of which is well known. He caused to be constructed one hundred and sixty-eight little mirrors six inches by eight, and directing their rays towards a point, succeeded in igniting a body at a considerable distance. By this he discovered a new principle, viz: that the action of the solar rays reflected is in direct ratio of the diameter of the focus; proving, moreover, that by multiplying the mirrors, an indefinite line of combustion might be established.
Can we infer, however, from these experiments of Buffon, that Archimedes actually destroyed the Roman galleys? We think not; considering the silence of the Roman writers on the subject, and the progress of science in the time of Buffon, with reference to its discoveries in the time of the Siege of Syracuse by Marcellus. Whether this mirror existed or not, however, Archimedes must be admitted to be one of the greatest geniuses the World of Science ever produced.