]

[Footnote 1605: T. Lewis, _Observatory_, vol. xvi., p. 312.]

[Footnote 1606: _Harvard Annals_, vol. xiv., pt. i., 1884.]

[Footnote 1607: _Observatory_, vol. viii., p. 309.]

[Footnote 1608: _Month. Not._, vol. xlvi., p. 277.]

[Footnote 1609: _Harvard Annals_, vol. xxxiv.]

[Footnote 1610: _Ibid._, vol. xlv.]

[Footnote 1611: _Carte Phot. du Ciel. Reunion du Comite Permanent_,
Paris, 1891, p. 100.]

[Footnote 1612: _Essays_ (2nd ser.), _The Nebular Hypothesis_.]

[Footnote 1613: _On the Plurality of Worlds_, p. 214 (2nd ed.).]

[Footnote 1614: Proctor, _Month. Not._, vol. xxix., p. 342.]

[Footnote 1615: This remark was first made by J. Michell, _Phil.
Trans._, vol. lvii., p. 25 (1767).]

[Footnote 1616: _Pop. Astr._, No. 45.]

[Footnote 1617: _Astroph. Jour._, vol. i., p. 220.]

[Footnote 1618: _Month. Not._, vols. xxxi., p. 175; xxxii., p. 1.]

[Footnote 1619: _The Stars_, p. 273.]

[Footnote 1620: _System of the Stars_, p. 384; _Old and New Astronomy_,
p. 749 (Ranyard).]

[Footnote 1621: _Astroph. Jour._, vol. xii., p. 156.]

[Footnote 1622: _Publ. Astr. Pac. Soc._, vol. ii., p. 242.]

[Footnote 1623: _Month. Not._, vol. li., pp. 40, 97. For reproductions
of some of the photographs in question, see _Knowledge_, vol. xiv., p.
50.]

[Footnote 1624: _Astr. Nach._, No. 3,048; _Observatory_, vol. xiv., p.
301.]

[Footnote 1625: _Proc. Roy. Inst._, May 29, 1891 (Gill).]

[Footnote 1626: _Annals Cape Obs._, iii., Introduction, p. 22.]

[Footnote 1627: _Proc. Roy. Soc._, vol. xviii., p. 169.]

[Footnote 1628: _Astr. Nach._, No. 3,456; _Observatory_, vol. xxi., p.
65; Newcomb, _The Stars_, p. 80.]

[Footnote 1629: _Month. Not._, vol. xl., p. 249.]

CHAPTER XIII

_METHODS OF RESEARCH_

Comparing the methods now available for astronomical inquiries with
those in use forty years ago, we are at once struck with the fact that
they have multiplied. The telescope has been supplemented by the
spectroscope and the photographic camera. Now, this really involves a
whole world of change. It means that astronomy has left the place where
she dwelt apart in rapt union with mathematics, indifferent to all
things on earth save only to those mechanical improvements which should
aid her to penetrate further into the heavens, and has descended into
the forum of human knowledge, at once a suppliant and a patron,
alternately invoking help fr