by using parabolic, hyperbolic or elliptical mirrors, but that I could use them upon objects at a much greater distance. With five mirrors I could obtain these effects at a distance of 100 feet, but what terrible phenomena would have taken place had I used one thousand instead of five?” He ends by begging mathematicians to experiment in this direction with greater care than they had hitherto done. After Kircher we may cite as an experimentalist with these terrible instruments the French philosopher Villette, who constructed several mirrors, in direct imitation of those of Archimedes, for Louis XIV. and other sovereigns. The _Journal des Savants_ for 1679 gives an account of his principal metallic burning mirror in the most eulogistic terms, adding an instance of ignorance which is singularly quaint and curious. It is of the fourth and most perfect of Villette’s mirrors that the _Journal des Savants_ speaks, the first having been bought by Tavernier, and presented to the Shah of Persia, who considered it as one of the rarest and most precious curiosities that he possessed: the second was sold to the King of Denmark, and the third was given by M. Villette to Louis XIV., from whom he received the praises and rewards that were due to his talent and perseverance. “It was thirty-four inches in diameter, and vitrified flints and bricks almost instantaneously, no matter how large they were. It consumed the greenest wood, burning it to ashes in an instant, and fused the most refractory metals with equal ease and quickness. Steel, no matter how hard, resisted its power no more than other metals, and melted so quickly that one part burnt away in inconceivably brilliant sparks, some of them forming stars as large as a franc piece, leaving a flowing mass of metal behind. The last made by Villette was still more powerful, being larger and more carefully made. It was forty-four inches in diameter, and three inches and a line deep. Its burning point, or focus, was situated at a distance of three feet seven inches from the surface, and was apparently as large as a five-sou piece; and it was at this spot, where the rays of light and heat were concentrated into so small a space, that the wonderful effects of its violent power became manifest, the spot of light being of such brilliancy that the eyes could no more withstand its brightness than that of the sun. Besides the property of burning which it possessed in so wonderful a degree, it was capable of exhibiting other effects just as curious as those already related. It had the power of sending the images of objects to a distance of fifteen feet or more, so that a man looking at himself in this mirror with a stick or sword in his hand, saw the image of them suspended in the air, apparently ready to strike the observer. On seeing such an effect for the first time, the observer could hardly fail to experience the greatest surprise, and even fear; and it is stated that the king having placed himself, sword in hand,