[454] This is not, however, invariably the case, as pointed out by Mr. Denning in The Observatory, 1885, p. 340.

[455] The Observatory, vol. 8 (1885), pp. 246-7.

[456] Harvard College Observatory Annals, vol. xlviii. No. 5.

[457] Popular Astronomy, vol. 15 (1907), p. 529.

[458] Cape Observations, p. 77.

[459] Monthly Notices, R.A.S., March, 1899.

[460] Nature, February 13, 1890.

[461] Popular Astronomy, vol. 15 (1907), p. 530.

[462] Photographs of Star-Clusters and Nebulæ, vol. ii. p. 17.

[463] Monthly Notices, R.A.S., May 9, 1856.