ilson but the Lick Observatory to which we have to give the honour. The
eminent director of this observatory, W. W. CAMPBELL, has in a high
degree developed the accuracy in the determination of radial velocities
and has moreover carried out such determinations in a large scale. The
"Bulletin" No. 229 (1913) of the Lick Observatory contains the radial
velocity of 915 stars. At the observatory of Lund, where as far as
possible card catalogues of the attributes of the stars are collected,
GYLLENBERG has made a catalogue of this kind for the radial velocities.
The total number of stars in this catalogue now amounts to 1640.[14]

28. Finally I shall briefly mention some comprehensive works on more
special questions regarding the stellar system.

On _variable stars_ there is published every year by HARTWIG in the
"Vierteljahrschrift der astronomischen Gesellschaft" a catalogue of all
known variable stars with needful information about their minima &c.
This is the completest and most reliable of such catalogues, and is
always up to date. A complete historical catalogue of the variables is
given in "Geschichte und Literatur des Lichtwechsels der bis Ende 1915
als sicher veraenderlich anerkannten Sterne nebst einem Katalog der
Elemente ihres Lichtwechsels" von G. MUeLLER und E. HARTWIG. Leipzig
1918, 1920.

On _nebulae_ we have the excellent catalogues of DREYER, the "New
General Catalogue" (N. G. C.) of 1890 in the "Memoirs of the
Astronomical Society" vol. 49, the "Index catalogues" (I. C.) in the
same memoirs, vols. 51 and 59 (1895 and 1908). These catalogues contain
all together 13226 objects.

Regarding other special attributes I refer in the first place to the
important Annals of the Harvard Observatory. Other references will be
given in the following, as need arises.

FOOTNOTES:

[Footnote 7: "Bonner Sternverzeichnis" in den Astronomischen
Beobachtungen auf der Sternwarte zu Bonn, Dritter bis Fuenfter Band. Bonn
1859-62.]

[Footnote 8: "Bonner Durchmusterung", Vierte Sektion. Achter Band der
Astronomischen Beobachtungen zu Bonn, 1886.]

[Footnote 9: "The Cape Photographic Durchmusterung" by DAVID GILL and J.
C. KAPTEYN, Annals of the Cape Observatory, vol. III-V (1896-1900).]

[Footnote 10: "Cordoba Durchmusterung" by J. THOME. Results of the
National Argentine Observatory, vol. 16, 17, 18, 21 (1894-1914).]

[Footnote 11: Aph. J., vol. 36.]

[Footnote 12: H. A., vol. 71.]

[Footnote 13: H. A., vol. 91, 92