evidence in support of his opinion.  “Moschopalus,” he says, “an ancient grammarian, mentions four instruments with which the astronomers of antiquity were accustomed to observe the stars—­the catoptron, the dioptron, the eisoptron and the enoptron.”  He supposes the catoptron to have been the same with the astrolabe.  “The dioptron seems to have been so named from a tube through which the observer looked.  Were the other two instruments named from objects being reflected in a mirror placed within them?  Aristotle says that the Greeks employed mirrors when they surveyed the celestial appearances.  May we not conclude from this circumstance that astronomers were not always satisfied with looking through empty tubes?” He thinks the ancients were acquainted with lenses and has collected passages from various writers which corroborate his opinion, besides referring to the numerous uses to which glass was applied in the most remote ages.  He goes on to say: 

“Some of the observations of the ancients must appear very extraordinary, if magnifying glasses had never been known among them.  The boldness with which the Pythagoreans asserted that the surface of the moon was diversified by mountains and valleys can hardly be accounted for, unless Pythagoras had been convinced of the fact by the help of telescopes, which might have existed in the observatories of Egypt and Chaldea before those countries were conquered and laid waste by the Persians.  Pliny (L. 11) says that 1600 stars had been counted in the 72 constellations, and by this expression I can only understand him to mean the 72 dodecans into which the Egyptians and Chaldeans divided the zodiac.  Now this number of stars could never have been counted in the zodiac without the assistance of glasses.  Ptolemy reckoned a much less number for the whole heavens The missionaries found many more stars marked in the Chinese charts of the heavens than formerly existed in those which were in use in Europe.  Suidas, at the word {Greek} (glass), indicates, in explaining a passage in Aristophanes, that burning mirrors were occasionally made of glass.  Now how can we suppose burning mirrors to have been made of glass without supposing the magnifying powers of glass to have been known?  The Greeks, as Plutarch affirms, employed metallic mirrors, either plane, or convex, or concave, according to the use for which they were intended.  If they could make burning mirrors of glass, they could have given any of these forms to glass.  How then could they have avoided observing that two glasses, one convex and the other concave, placed at a certain distance from each other, magnified objects seen through them?  Numerous experiments must have been made with concave and convex glasses before burning mirrors made of glass could have been employed.  If astronomers never knew the magnifying powers of glass, and never placed lenses in the tubes of the dioptrons, what does Strabo (L. 3, c. 138) mean when he says:  ’Vapours produce the same effects as the tubes in magnifying objects of vision by refraction?’”