[215] See Newcomb's Pop. Astr., p. 359. The error of Uranus amounted, in 1844, to 2′; but even the tailor of Breslau, whose extraordinary powers of vision Humboldt commemorates (Kosmos, Bd. ii., p. 112), could only see Jupiter's first satellite at its greatest elongation, 2′ 15′. He might, however, possibly have distinguished two objects of equal lustre at a lesser interval.
[216] J. W. L. Glaisher, Observatory, vol. xv., p. 177.
[217] Mem. R. A. S., vol. xvi., p. 399.
[218] For an account of D'Arrest's share in the detection see Copernicus, vol. ii., pp. 63, 96.
[219] Mem. R. A. S., vol. xvi., p. 412.
[220] He had recorded the places of 3,150 stars (three of which were different positions of the planet), and was preparing to map them, when, October 1, news of the discovery arrived from Berlin. Prof. Challis's Report, quoted in Obituary Notice, Month. Not., Feb., 1883, p. 170.
[221] See Airy in Mem. R. A. S., vol. xvi., p. 411.
[222] He died January 21, 1892, in his 71st year.
[223] Ledger, The Sun, its Planets and their Satellites, p. 414.
[224] Presented by the Misses Lassell, after their father's death, to the Greenwich Observatory.