There is a story of an eminent astronomer who had been on several eclipse expeditions, and yet was heard to remark that he had never seen a total eclipse of the sun. "But your observations of several eclipses are on record," it was objected. "Certainly, I have on several occasions made observations, but I have always been too busy to look at the eclipse." He was probably in a dark tent taking photographs or using a spectroscope during the totality. This was observing an eclipse without seeing it! Humboldt gives the credit of the invention of the telescope to Hans Lippershey, a native of Wesel and a spectacle-maker at Middleburgh; to Jacob Adreaansz, surnamed Metius, who is also said to have made burning-glasses of ice; and to Zachariah Jansen.[497] With reference to the parabolic figure of the large mirrors of reflecting telescopes, Dr. Robinson remarked at the meeting of the British Association at Cork in 1843, "between the spherical and parabolic figures the extreme difference is so slight, even in the telescope of 6-feet aperture [Lord Rosse's] that if the two surfaces touched at their vertex, the distance at the edge would not amount to the 1/10000th of an inch, a space which few can measure, and none without a microscope."[498] In the year 1758, Roger Long, Lowndean Professor of Astronomy at Cambridge, constructed an "orrery" on a novel principle. It was a hollow metal sphere of about 18 feet in diameter with its fixed axis parallel to the earth's axis. It was rotated, by means of a winch and rackwork. It held about thirty persons in its interior, where astronomical lectures were delivered. The constellations were painted on the interior surface; and holes pierced through the shell and illuminated from the outside represented the stars according to their different magnitudes. This ingenious machine was much neglected for many years, but was still in existence in Admiral Smyth's time, 1844.[499] A "temporary star" is said to have been seen by Hepidanus in the constellation Aries in either 1006 or 1012 A.D. The late M. Schönfeld, a great authority on variable stars, found from an Arabic and Syrian chronicle that 1012 is the correct year (396 of the Hegira), but that the word translated Aries would by a probable emendation mean Scorpio. The word in the Syrian record is not the word for Aries.[500] Mr. Heber D. Curtis finds that the faintest stars mentioned in Ptolemy's Catalogue are about 5·38 magnitude on the scale of the Harvard _Photometric Durchmustering_.[501] Heis and Houzeau saw stars of 6-7 magnitude (about 6·4 on Harvard scale). The present writer found that he could see most of Heis' faintest stars in the west of Ireland (Co. Sligo) without optical aid (except short-sighted spectacles). With reference to the apparent changes in the stellar heavens produced by the precession of the equinoxes, Humboldt says--