[328] Airy, Month. Not., vol. ix., p. 120.
[329] Astronomical Journal (Gould's), vol. ii., p. 97.
[330] Ibid., p. 160.
[331] Lord Rosse in Phil. Trans., vol. cxl., p. 505.
[332] No. 2343 of Herschel's (1864) Catalogue. Before 1850 a star was visible in each of the two larger openings by which it is pierced; since then, one only. Webb, Celestial Objects (4th ed.), p. 409.
[333] Mem. Am. Ac., vol. iii., p. 87; Astr. Nach., No. 611.
[334] Pop. Astr., p. 145.
[335] This statement must be taken in the most general sense. Supplementary observations of great value are now made at Greenwich with the altitude and azimuth instrument, which likewise served Piazzi to determine the places of his stars; while a "prime vertical instrument" is prominent at Pulkowa.
[336] As early as 1620, according to R. Wolf (Ges. der Astr., p. 587), Father Scheiner made the experiment of connecting a telescope with an axis directed to the pole, while Chinese "equatoreal armillæ," dating from the thirteenth century, existed at Pekin until 1900, when they were carried off as "loot" to Berlin. J. L. E. Dreyer, Copernicus, vol. i., p. 134.
[337] Miscellaneous Works, p. 350.