ound 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.

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During the five years until 1650 the department of acoustics came
under his consideration, so that in that year we have from his pen a
treatise called "Musurgia Universalis," with the subtitle, "The Art of
Harmony and Discord; a treatise on the whole doctrine of sound with
the philosophy of music treated from the standpoint of practical as
well as theoretic science." During the next five years astronomy was
his special hobby, and the result was in 1656 a treatise on astronomy
called "Iter Celeste." This contained a description of the earth and
the heavens and discussed the nature of the fixed and moving stars,
with various considerations as to the composition and structure of
these bodies. A second volume on this subject appeared in 1660.

The variety of Father Kircher's interests in science was not yet
exhausted, however. Five years after the completion of his two volumes
on astronomy there came one on "Mundus Subterraneus." This treated of
the modern subjects of geology, metallurgy, and mineralogy, as well as
the chemistry of minerals. It also contained a treatise on animals
that live under the ground, and on insects. This was considered one of
the author's greatest books, and the whole of it was translated into
French, whilst abstracts from it, especially the chapters on poisons,
appeared in most of the other languages of Europe. Part of it was
translated even into English, though seventeenth-century Englishmen
were loath to draw their inspiration from Jesuit writers.

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Jesuits were, however, a