BURNING MIRRORS.
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subsequent experiments have been made by which it isfound that specula, ingeniously constructed, may effectignition at as great a distance as it was probable the shipsof the hostile visitants might lie from the shore. And witha view to vindicate the ancient historians previously named,none felt more zealous than did the eminent and learnedKircher, who went with his pupil Schottus, to the scene ofthe historical transaction, where Kircher made many ex-periments in order to validate the credibility of his histori-cal predecessors. Conceiving the concave specula of theancients were sections of a parabola, he began with combiningseveral of this figure; but failing of success, he next tried theeffect of a number of plane mirrors ; and with only fivemirrors of the same size, placed in a frame, he contrived tothrow the rays reflected from them to the distance of morethan 100 feet; and by these means he produced such adegree of heat, as led him to conclude that by increasingtheir number, he could set fire to any inflammable substanceat a greater distance.
The ideas of the master and his pupil both concurred, onexamining the local spot, that it was probable the galleysof Marcellus could not be much more than thirty paces fromthe machinery of Archimedes . This they presumed, in totalignorance of the exquisite perfection to w hich it is proba-ble that able mathematician had brought his invention.M. Bufton, though totally ignorant of those historical testi-monies relative to the effect of the invention of Archimedes ,and also ignorant of the attempt of Kircher in its vindica-tion, has long since, by a similar contrivance, sufficientlyevinced the practicability of the operation.
l)r. Wolfe, in the year 1768, after describing some para-bolic mirrors of M. lloesen, of Dresden , offers a con-jecture that those of Archimedes might be of this kind;since it is not difficult to describe a parabola whoseparameter is 2000 feet; and that rays reflected from such aspeculum might be received by a lens, and having beenbrought to a focus, transmitted parallel to any distance.But it appears that he was not aware of the experimentwhich Kepler and Dechaler had made, showing, that norays could be conveyed parallel to one another, exceptthose which proceed from the same point in the sun’sdisk. Datens du Miroir Ardent d’Archimedie. Paris, 1755.Phil. Trans, vol. xlviii. p. 621, &c. et Ibid. vol. lix. p. 8.
Those mirrors, the most remarkable which the modernshave constructed, shall now be mentioned. That of Magine,twenty inches in diameter; of Septala, of Milan, near three