pkins.
1840, March 2 Death of Olbers.
1840 First attempt to photograph the moon by J. W. Draper.
1842 Doppler enounces principle of colour-change by motion.
1842 Conclusion of Baily's experiments in weighing the Earth.
1842, July 8 Total solar eclipse. Corona and prominences observed
by Airy, Baily, Arago, and Struve.
1843, Feb. 27 Perihelion-passage of great comet.
1845, February Completion of Parsonstown reflector.
1845, April Discovery with it of spiral nebulae.
1845, April 2 Daguerreotype of the sun taken by Foucault and Fizeau.
1845, Oct. 21 Place of Neptune assigned by Adams.
1845, Dec. 8 Discovery of Astraea by Hencke.
1845, Dec. 29 Duplication of Biela's comet observed at Yale College.
1846 Melloni's detection of heating effects from moonlight.
1846, March 17 Death of Bessel.
1846, Sept. 23 Discovery of Neptune by Galle.
1846, Oct. 10 Neptune's satellite discovered by Lassell.
1847 Publication of Sir J. Herschel's _Results of
Observations at the Cape of Good Hope_.
1847 Cyclonic theory of sun-spots stated by him.
1848 J. R. Mayer's meteoric hypothesis of solar conservation.
1848 Motion-displacements of Fraunhofer lines adverted to
by Fizeau.
1848, April 27 New Star in Ophiuchus observed by Hind.
1848, Sept. 19 Simultaneous discovery of Hyperion by Bond and Lassell.
1849 First experimental determination of the velocity of
light (Fizeau).
1850, July 17 Vega photographed at Harvard College.
1850, Nov. 15 Discovery by Bond of Saturn's dusky ring.
1851 O. Struve's first measurements of Saturn's ring-system
1851, July 28 Total solar eclipse observed in Sweden.
1851, Oct. 24 Discovery by Lassell of two inner Uranian satellites.
1851 Schwabe's discovery of sun-spot periodicity published by
Humboldt.
1852, May 6 Coincidence of magnetic and sun-spot periods announced
by Sabine.
1852, Oct. 11 Variable nebula in Taurus discovered by Hind.
1852 Lassell's two-foot reflector transported to Malta.
1853 Adams shows Laplace's explanation of the moon's
acceleration to be incomplete.
1854 Han