Other great photographic star charts have been carried through by the Harvard Observatory, with the annex at Arequipa, Peru, employing the Bruce photographic telescope, a doublet with 24-inch lenses; also Kapteyn of Groningen has catalogued about 300,000 stars on plates taken at Cape Town. Charting and cataloguing the stars, both visually and photographically, is a work that will never be entirely finished. Improvements in processes will be such that it can be better done in the future than it is now, and the detection of changes in the fainter stars and investigation of their motions will necessitate repetition of the entire work from century to century. The origin of the names of individual stars is a question of much interest. The constellation figures form the basis of the method, and the earliest names were given according to location in the especial figure; as for instance, Cor Scorpii, the heart of the Scorpion, later known as Antares or Alpha Scorpii. The Arabians adopted many star names from the Greeks, and gave about a hundred special names to other stars. Some of these are in common use to-day, by navigators, observers of meteors and of variable stars. Sirius, Vega, Arcturus, and a few other first magnitude stars, are instances. But this method is quite insufficient for the fainter stars whose numbers increase so rapidly. Bayer, a contemporary of Galileo, originated our present system, which also employs the names of the constellations, the Latin genitive in each case, prefixed by the small letters of the Greek alphabet, from alpha to omega, in order of decreasing brightness; and followed by the Roman letters when the Greek alphabet is exhausted. If there were still stars left in a constellation unnamed, numbers were used, first by Flamsteed, Astronomer Royal; and numbers in the order of right ascension in various catalogues are used to designate hundreds of other stars. The vast bulk of the stars are, however, nameless; but about one million are identifiable by their positions (right ascension and declination) on the celestial sphere. CHAPTER XLVI THE SUN'S MOTION TOWARD LYRA