Father Kircher began his career as a writer on science at the early age of twenty-seven, when he issued his first work on magnetism. The title of this volume, "Ars Magnesia tum Theorematice tum Problematice Proposita," shows that the subject was not treated entirely from a speculative standpoint. Indeed, in the preface he states that he hopes that the principal value of the book will be found in the fact that the knowledge of magnetism is presented by a new method, with special demonstrations, and that the conclusions are confirmed by various practical uses and long-continued experience with magnets of various kinds. Although it may be a source of great surprise, Father Kircher's genius was essentially experimental. He has been spoken of not infrequently as a man who collected the scientific information of his time in such a way as to display, as says the _Encyclopedia Britannica_, "a wide and varied learning, but that he was a man singularly devoid of judgment and critical discernment." He was in some respects the direct opposite of the opinion thus expressed, since his learning was always of a practical character, and there are very few subjects in this writing which he has not himself illustrated by means of new and ingenious experiments. Perhaps the best possible proof of this is to be {121} found in the fact that his second scientific work was on the construction of sun-dials, and that one of the discoveries he himself considered most valuable was the invention of a calculating machine, as well as of a complicated arrangement for illustrating the positions of the stars in the heavens. He constructed, moreover, a large burning-glass in order to demonstrate the possibility of the story told of Archimedes, that he had succeeded in burning the enemy's ships in the harbor at Syracuse by means of a large lens. But Father Kircher's surest claim to being a practical genius is to be found in his invention of the magic lantern. It was another Jesuit, Aquilonius, in his work on optics, issued in 1613, who had first sought to explain how the two pictures presented to the two eyes are fused into one, and it was in a practical demonstration of this by means of lenses that Kircher hit upon the invention of the projecting stereoscope. After his call to Rome our subject continued his work on magnetism, and in 1641 issued a further treatise on the subject called "Magnes" or "De Arte Magnetica." While he continued to teach Oriental languages and issued in 1644 a book with the title "Lingua AEgyptiaca Restituta," he also continued to apply himself especially to the development of physical science. Accordingly in 1645 there appeared his volume "Ars Magna Lucis et Umbrae." This was a treatise on light, illustrated, as was his treatise on magnetism, by many original experiments and demonstrations. {122}