lin Soc._, vol. iii., p. 61.]

[Footnote 1649: _Observatory_, vol. vii., p. 167.]

[Footnote 1650: Loewy, _Bull. Astr._, t. i., p. 265.]

[Footnote 1651: _Phil. Trans._, vol. clxxi., p. 653.]

[Footnote 1652: Janssen, _L'Astronomie_, t. ii., p. 121.]

[Footnote 1653: Rev. A. L. Cortie, _Astr. and Astrophysics_, vol. xi.,
p. 400.]

[Footnote 1654: _Phil. Mag._, vol. xiii., 1882, p. 469.]

[Footnote 1655: _Bull. Astr._, t. iii., p. 331.]

APPENDIX

TABLE I

CHRONOLOGY, 1774-1893

1774, March 4 Herschel's first observation. Subject, the Orion Nebula.
1774 Sun-spots geometrically proved to be depressions by
Wilson.
1774 First experimental determination of the earth's mean
density by Maskelyne.
1781, March 13 Discovery of Uranus.
1782 Herschel's first Catalogue of Double Stars.
1783 Herschel's first investigation of the sun's movement
in space.
1783 Goodricke's discovery of Algol's law of variation.
1784 Analogy between Mars and the Earth pointed out by
Herschel.
1784 Construction of the Heavens investigated by Herschel's
method of star-gauging. "Cloven-disc" plan of the
Milky Way.
1784 Discovery of binary stars anticipated by Michell.
1786 Herschel's first Catalogue of Nebulae.
1787, Jan. 11 Discovery by Herschel of two Uranian moons
(Oberon and Titania).
1787, Nov. 19 Acceleration of the moon explained by Laplace.
1789 Herschel's second Catalogue of Nebulae, and
classification by age of these objects.
1789 Completion of Herschel's forty-foot reflector.
1789, Aug. 28 His discovery with it of the two inner Saturnian
and Sept. 17 satellites.
1789 Repeating-circle invented by Borda.
1789 Five-foot circle constructed by Ramsden for Piazzi.
1790 Maskelyne's Catalogue of thirty-six fundamental stars.
1791 Herschel propounds the hypothesis of a fluid
constitution for nebulae.
1792 Atmospheric refraction in Venus announced by Schroeter.
1794 Rotation-period of Saturn fix