A Popular History of Astronomy During the Nineteenth Century

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 Nebulæ.
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 Nebulæ, and classification by age of these objects.
1789	Completion of Herschel’s forty-foot reflector.
1789, Aug. 28 and Sept. 17	His discovery with it of the two inner Saturnian 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 nebulæ.
1792	Atmospheric refraction in Venus announced by Schröter.
1794	Rotation-period of Saturn fixed by Herschel at 10h. 16m.
1795	Herschel’s theory of the solar constitution.
1796	Herschel’s first measures of comparative stellar brightness
1796	Laplace’s Nebular Hypothesis published in Exposition du Système du Monde.
1797	Publication of Olbers’s method of computing cometary orbits.
1798	Retrograde motions of Uranian satellites detected by Herschel.
1799	Publication of first two volumes of Mécanique Céleste.
1799, May 7	Transit of Mercury observed by Schröter.
1799, Nov. 12	Star-shower observed by Humboldt at Cumana.
1800	Monatliche Correspondenz started by Von Zach.
1800	Invisible heat-rays detected in the solar spectrum by Herschel.
1801, Jan. 1	Discovery of Ceres by Piazzi.
1801	Publication of Lalande’s Histoire Céleste.
1801	Investigation by Herschel of solar emissive variability in connection with spot-development.
1802, March 28	Discovery of Pallas by Olbers.
1802	Herschel’s third Catalogue of Nebulæ.
1802	Herschel’s discovery of binary stars.
1802	Marks of clustering in the Milky Way noted by Herschel.
1802	Wollaston records seven dark lines in the solar spectrum.
1802, Nov. 9	Transit of Mercury observed by Herschel.
1804, Sept. 2	Transit of Mercury observed by Herschel.
1804	Foundation of Optical Institute at Munich.
1805	Herschel’s second determination of the solar apex.
1807, March 29	Discovery of Vesta by Olbers.
1811	Herschel’s theory of the development of stars from nebulæ.
1811, Feb. 9	Death of Maskelyne. Pond appointed to succeed him as Astronomer-Royal.
1811, Sept. 12	Perihelion passage of great comet.
1814	Herschel demonstrates the irregular distribution of stars in space.
1815	Fraunhofer maps 324 dark lines in the solar spectrum.
1818	Publication of Bessel’s Fundamenta Astronomiæ.
1819	Recognition by Encke of the first short-period comet.
1819, June 26	Passage of the earth through the tail of a comet.
1820	Foundation of the Royal Astronomical Society.
1821	Foundation of Paramatta Observatory.
1821, September	First number of Astronomische Nachrichten.
1822, May 24	First calculated return of Encke’s comet.
1822, August 25	Death of Herschel.
1823	Bessel introduces the correction of observations for personal equation.
1823	Fraunhofer examines the spectra of fixed stars.
1824	Distance of the sun concluded by Encke to be 95-1/4 million miles.
1824	Publication of Lohrmann’s Lunar Chart.
1824	Dorpat refractor mounted equatoreally.
1826	Commencement of Schwabe’s observations of sun-spots.
1826, Feb. 27	Biela’s discovery of a comet.
1827	Orbit of a binary star calculated by Savary.
1829	Completion of the Royal Observatory at the Cape of Good Hope.
1829	The Königsberg heliometer mounted.
1830	Publication of Bessel’s Tabulæ Regiomontanæ.
1832	Discovery by Brewster of “atmospheric lines” in the solar spectrum.
1833	Magnetic observatory established at Göttingen.
1833, Nov. 12, 13	Star-shower visible in North America.
1833	Completion of Sir J. Herschel’s survey of the northern heavens.
1834, Jan. 16	Sir J. Herschel’s landing at the Cape.
1835, September	Airy appointed Astronomer-Royal in succession to Pond.
1835, Nov. 16	Perihelion passage of Halley’s comet.
1837	Solar movement determined by Argelander.
1837	Bessel’s application of the heliometer to measurements of stellar parallax.
1837	Publication of Beer and Mädler’s Der Mond.
1837, Dec. 16	Outburst of η Carinæ observed by Sir J. Herschel.
1837	Thermal power of the sun measured by Herschel and Pouillet.
1838	Parallax of 61 Cygni determined by Bessel.
1839, Jan. 9	Parallax of α Centauri announced by Henderson.
1839	Completion of Pulkowa Observatory.
1839	Solidity of the earth concluded by Hopkins.
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 nebulæ.
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 Astræa 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 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	Hansen infers from lunar theory a reduced value for the distance of the sun.
1854	Helmholtz’s “gravitation theory” of solar energy.
1856	Piazzi Smyth’s observations on the Peak of Teneriffe.
1857	Saturn’s rings shown by Clerk Maxwell to be of meteoric formation.
1857, April 27	Double-star photography initiated at Harvard College.
1858	Solar photography begun at Kew.
1858, Sept. 30	Perihelion of Donati’s comet.
1859	Spectrum analysis established by Kirchhoff and Bunsen.
1859	Carrington’s discovery of the compound nature of the sun’s rotation.
1859, Sept. 1	Luminous solar outburst and magnetic storm.
1859, Oct. 19	Merope nebula discovered by Tempel.
1859, Dec. 15	Chemical constitution of the sun described by Kirchhoff.
1860, Feb. 27	Discovery by Liais of a “double comet.”
1860, May 21	New star in Scorpio detected by Auwers.
1860, July 18	Total solar eclipse observed in Spain. Prominences shown by photography to be solar appendages.
1861, June 30	The earth involved in the tail of a great comet.
1861-1862	Kirchhoff’s map of the solar spectrum.
1862	Solar hydrogen-absorption recognised by Ångström.
1862, Jan. 31	Discovery by Alvan G. Clark of the companion of Sirius.
1862	Foucault determines the sun’s distance by the velocity of light.
1862	Opposition of Mars. Determination of solar parallax.
1862	Completion of Bonner Durchmusterung.
1863	Secchi’s classification of stellar spectra.
1863	Foundation of the German Astronomical Society.
1864, March 5	Rotation period of Mars determined by Kaiser.
1864	Huggins’s first results in stellar spectrum analysis.
1864, Aug. 5	Spectroscopic examination of Tempel’s comet by Donati shows it to be composed of glowing gas.
1864, Aug. 29	Discovery by Huggins of gaseous nebulæ.
1864	Value of 91,000,000 miles adopted for the sun’s distance.
1864	Croll’s explanation of glacial epochs.
1864, Nov. 23	Death of Struve.
1865, Jan. 4	Spectroscopic observation by Huggins of the occultation of ε Piscium.
1865, Jan. 16	Faye’s theory of the solar constitution.
1865	Kew results published.
1865	Zöllner argues for a high temperature in the great planets.
1866	Identity of the orbits of the August meteors and of comet 1862 iii. demonstrated by Schiaparelli.
1866	Delaunay explains lunar acceleration by a lengthening of the day through tidal friction.
1866, March 4	Spectroscopic study of the sun’s surface by Lockyer.
1866, March 12	New star in Corona Borealis detected by Birmingham.
1866, October	Schmidt announces the disappearance of the lunar crater Linné.
1866, Nov. 13	Meteoric shower visible in Europe.
1867	Period of November meteors determined by Adams.
1867, Aug. 29	Total solar eclipse. Minimum sun-spot type of corona observed by Grosch at Santiago.
1867	Discovery of gaseous stars in Cygnus by Wolf and Rayet.
1868, February	Principle of daylight spectroscopic visibility of prominences started by Huggins.
1868, Aug. 18	Great Indian eclipse. Spectrum of prominences observed.
1868, Aug. 19	Janssen’s first daylight view of a prominence.
1868, Oct. 26	Lockyer and Janssen independently announce their discovery of the spectroscopic method.
1868	Doppler’s principle applied by Huggins to measure stellar radial movements.
1868	Publication of Ångström’s map of the normal solar spectrum.
1868	Spectrum of Winnecke’s comet found by Huggins to agree with that of olefiant gas.
1869, Feb. 11	Tenuity of chromospheric gases inferred by Lockyer and Frankland.
1869, Feb. 13	Huggins observes a prominence with an “open slit.”
1869, Aug. 7	American eclipse. Detection of bright-line coronal spectrum.
1870	Mounting of Newall’s 25-inch achromatic at Gateshead.
1870	Proctor indicates the prevalence of drifting movements among the stars.
1870	A solar prominence photographed by Young.
1870, Dec. 22	Sicilian eclipse. Young discovers reversing layer.
1871, May 11	Death of Sir J. Herschel.
1871, June 9	Line-displacements due to solar rotation detected by Vogel.
1871, Dec. 12	Total eclipse visible in India. Janssen observes reflected Fraunhofer lines in spectrum of corona.
1872	Conclusion of a three years’ series of observations on lunar heat by Lord Rosse.
1872	Spectrum of Vega photographed by H. Draper.
1872	Faye’s cyclonic hypothesis of sun-spots.
1872	Young’s solar-spectroscopic observations at Mount Sherman.
1872	Cornu’s experiments on the velocity of light.
1872, Nov. 27	Meteoric shower connected with Biela’s comet.
1873	Determination of mean density of the earth by Cornu and Baille.
1873	Solar photographic work begun at Greenwich.
1873	Erection of 26-inch Washington refractor.
1874	Light-equation redetermined by Glasenapp.
1874	Vogel’s classification of stellar spectra.
1874, Dec. 8	Transit of Venus.
1876	Publication of Neison’s The Moon.
1876, Nov. 24	New star in Cygnus discovered by Schmidt.
1876	Spectrum of Vega photographed by Huggins. First use of dry gelatine plates in celestial photography.
1877, May 19	Klein observes a supposed new lunar crater (Hyginus N.).
1877	Measurement by Vogel of selective absorption in solar atmosphere.
1877, Aug. 16-17	Discovery of two satellites of Mars by Hall at Washington.
1877, Sept. 23	Death of Leverrier.
1877	Canals of Mars discovered by Schiaparelli.
1877	Opposition of Mars observed by Gill at Ascension. Solar parallax deduced = 8·78′.
1878, January	Stationary meteor-radiants described by Denning.
1878	Publication of Schmidt’s Charte der Gebirge des Mondes.
1878	First observations of Great Red Spot on Jupiter.
1878	Conclusion of Newcomb’s researches on the lunar theory.
1878, May 6	Transit of Mercury.
1878	Foundation of Selenographical Society.
1878, July 29	Total eclipse visible in America. Vast equatoreal extension of the corona.
1878, October	Completion of Potsdam Astrophysical Observatory.
1878, Dec. 12	Lockyer’s theory of celestial dissociation communicated to the Royal Society.
1879	Michelson’s experiments on the velocity of light.
1879	Publication of Gould’s Uranometria Argentina.
1879, November	Observations of the spectra of sun-spots begun at South Kensington.
1879, Dec. 5	Abney’s map of the infra-red solar spectrum presented to the Royal Society.
1879, Dec. 18	Ultra-violet spectra of white stars described by Huggins.
1879, Dec. 18	Communication of G. H. Darwin’s researches into the early history of the moon.
1880, Jan. 31	Discovery at Cordoba of a great southern comet.
1880	Conditions of Algol’s eclipses determined by Pickering.
1880	Pickering computes mass-brightness of binary stars.
1880, Sept. 30	Draper’s photograph of the Orion nebula.
1880	The bolometer invented by Langley.
1881, Jan. 20	Communication of G. H. Darwin’s researches into the effects of tidal friction on the evolution of the solar system.
1881	Langley’s observations of atmospheric absorption on Mount Whitney.
1881, June 16	Perihelion of Tebbutt’s comet.
1881, June 24	Its spectrum photographed by Huggins.
1881, June	Photographs of Tebbutt’s comet by Janssen and Draper.
1881, Aug. 15	Retirement of Sir George Airy. Succeeded by Christie.
1881, Aug. 22	Perihelion of Schaeberle’s comet.
1881	Publication of Stone’s Cape Catalogue for 1880.
1881	Struve’s second measures of Saturn’s ring-system.
1882	Newcomb’s determination of the velocity of light. Resulting solar parallax = 8·79′.
1882	Correction by Nyrén of Struve’s constant of aberration.
1882, March 7	Spectrum of Orion nebula photographed by Huggins.
1882, May 17	Total solar eclipse observed at Sohag in Egypt.
1882, May 27	Sodium-rays observed at Dunecht in spectrum of Comet Wells.
1882, June 10	Perihelion of Comet Wells.
1882, Sept. 17	Perihelion of Great Comet. Daylight detection by Common. Transit observed at the Cape.
1882, Sept. 18	Iron lines identified in spectrum by Copeland and J. G. Lohse.
1882, September	Photographs of comet taken at the Cape Observatory, showing a background crowded with stars.
1882, Dec. 6	Transit of Venus.
1882	Duplication of Martian canals observed by Schiaparelli.
1882	Completion by Loewy at Paris of first equatoreal Coudé.
1882	Rigidity of the earth concluded from tidal observations by G. H. Darwin.
1882	Experiments by Huggins on photographing the corona without an eclipse.
1882	Publication of Holden’s Monograph of the Orion Nebula.
1883, Jan. 30	Orion Nebula photographed by Common.
1883, May 6	Caroline Island eclipse.
1883, June 1	Great comet of 1882 observed from Cordoba at a distance from the earth of 470 million miles.
1883	Parallaxes of nine southern stars measured by Gill and Elkin.
1883	Catalogue of the spectra of 4,051 stars by Vogel.
1884, Jan. 25	Return to perihelion of Pons’s comet.
1884	Photometric Catalogue by Pickering of 4,260 stars.
1884	Publication of Gore’s Catalogue of Variable Stars.
1884	Publication of Faye’s Origine du Monde.
1884, Oct. 4	Eclipse of the moon. Heat-phases measured by Boeddicker at Parsonstown.
1884	Dunér’s Catalogue of Stars with Banded Spectra.
1884	Backlund’s researches into the movements of Encke’s comet.
1885, February	Langley measures the lunar heat-spectrum.
1885	Publication of Uranometria Nova Oxoniensis.
1885, Aug. 17	New star in Andromeda nebula discerned by Gully.
1885, Sept. 5	Thollon’s drawing of the solar spectrum presented to the Paris Academy.
1885, Sept. 9	Solar eclipse visible in New Zealand.
1885, Nov. 16	Photographic discovery by Paul and Prosper Henry of a nebula in the Pleiades.
1885, Nov. 27	Shower of Biela meteors.
1885	Thirty-inch achromatic mounted at Pulkowa.
1885	Publication of Rowland’s photographic map of the normal solar spectrum.
1885	Bakhuyzen’s determination of the rotation period of Mars.
1885	Stellar photographs by Paul and Prosper Henry.
1886, Jan. 26	Spectra of forty Pleiades simultaneously photographed at Harvard College.
1886, Feb. 5	First visual observation of the Maia nebula with Pulkowa 30-inch refractor.
1886, March	Photographs by the Henrys of the Pleiades, showing 2,326 stars with nebulæ intermixed.
1886, May	Photographic investigations of stellar parallax undertaken by Pritchard.
1886, May 6	Periodical changes in spectra of sun-spots announced by Pritchard.
1886, June 4	An international Photographic Congress proposed by Gill.
1886, Aug. 29	Total eclipse of the sun observed at Grenada.
1886, Oct. 1	Roberts’s photograph showing annular structure of the Andromeda nebula.
1886, Dec. 8	Roberts’s photograph of the Pleiades nebulosities.
1886	Solar heat-spectrum extended by Langley to below five microns.
1886, Dec. 28	Detection by Copeland of helium-ray in spectrum of the Orion nebula.
1886	Thirty-inch refractor mounted at Nice.
1886	Publication of Argentine General Catalogue.
1886	Completion of Auwers’s reduction of Bradley’s observations.
1886	Draper Memorial photographic work begun at Harvard College.
1886	Photographic detection at Harvard College of bright hydrogen lines in spectra of variables (Mira Ceti and U Orionis).
1887, Jan. 18	Discovery by Thome at Cordoba of a great comet belonging to the same group as the comet of 1882.
1887	Publication of Lockyer’s Chemistry of the Sun.
1887, April 16	Meeting at Paris of the International Astrophotographic Congress.
1887	Heliometric triangulation of the Pleiades by Elkin.
1887	L. Struve’s investigation of the sun’s motion, and redetermination of the constant of precession.
1887	Von Konkoly’s extension to 15° S. Dec. of Vogel’s spectroscopic Catalogue.
1887	Auwers’s investigation of the solar diameter.
1887	Publication of Schiaparelli’s Measures of Double Stars (1875-85).
1887, April 8	Death of Thollon at Nice.
1887, Aug. 19	Total eclipse of the sun. Shadow-path crossed Russia. Observations marred by bad weather.
1887, November	Langley’s researches on the temperature of the moon.
1887, Nov. 17	Lockyer’s Researches on Meteorites communicated to the Royal Society.
1887	Completion of 36-inch Lick refractor.
1888	Küstner’s detection of variations in the latitude of Berlin brought before the International Geodetic Association.
1888	Chandler’s first Catalogue of Variable Stars.
1888	Mean parallax of northern first magnitude stars determined by Elkin.
1888	Publication of Dreyer’s New General Catalogue of 7,844 nebulæ.
1888	Vogel’s first spectrographic determinations of stellar radial motion.
1888	Carbon absorption recognised in solar spectrum by Trowbridge and Hutchins.
1888, Jan. 28	Total eclipse of the moon. Heat-phases measured at Parsonstown.
1888, Feb. 5	Remarkable photograph of the Orion nebula spectrum taken at Tulse Hill.
1888, June 1	Activity of the Lick Observatory begun.
1888	Completion of Dr. Common’s 5-foot reflector.
1888	Heliometric measures of Iris for solar parallax at the Cape, Newhaven (U.S.A.), and Leipsic.
1888	Loewy describes a comparative method of determining constant of aberration.
1888	Presentation of the Dunecht instrumental outfit to the nation by Lord Crawford. Copeland succeeds Piazzi Smyth as Astronomer-Royal for Scotland.
1888, Sept. 12	Death of R. A. Proctor.
1889	Photograph of the Orion nebula taken by W. H. Pickering, showing it to be the nucleus of a vast spiral.
1889	Discovery at a Harvard College of the first-known spectroscopic doubles, ζ Ursæ Majoris and β Aurigæ.
1889	Eclipses of Algol demonstrated spectrographically by Vogel.
1889	Completion of photographic work for the Southern Durchmusterung.
1889	Boeddicker’s drawing of the Milky Way.
1889	Draper Memorial photographs of southern star-spectra taken in Peru.
1889	Pernter’s experiments on scintillation from the Sonnblick.
1889	H. Struve’s researches on Saturn’s satellites.
1889	Harkness’s investigation of the masses of Mercury, Venus, and the Earth.
1889	Heliometric measures of Victoria and Sappho at the Cape.
1889, Jan. 1	Total solar eclipse visible in California.
1889, Feb. 7	Foundation of the Astronomical Society of the Pacific.
1889, March	Investigation by Sir William and Lady Huggins of the spectrum of the Orion nebula.
1889, July-Aug.	First photographs of the Milky Way taken by Barnard.
1889, August 2	Observation by Barnard of four companions to Brooks’s comet.
1889, Nov. 1	Passage of Japetus behind Saturn’s dusky ring observed by Barnard.
1889, December	Schiaparelli announces synchronous rotation and revolution of Mercury.
1889, Dec. 22	Total eclipse of the sun visible in Guiana. Death of Father Perry, December 27.
1889	Spectrum of Uranus investigated visually by Keeler, photographically by Huggins.
1890	Long-exposure photographs of ring-nebula in Lyra.
1890	Determinations of the solar translation by L. Boss and O. Stumpe.
1890	Schiaparelli finds for Venus an identical period of rotation and revolution.
1890	Publication of Thollon’s map of the solar spectrum.
1890	Bigelow’s mathematical theory of coronal structures.
1890	Foundation of the British Astronomical Association.
1890	Measurements by Keeler at Lick of nebular radial movements.
1890	Janssen’s ascent of Mont Blanc, by which he ascertained the purely terrestrial origin of the oxygen-absorption in the solar spectrum.
1890	Newcomb’s discussion of the transits of Venus of 1761 and 1769.
1890	Spiral structure of Magellanic Clouds displayed in photographs taken by H. C. Russell of Sydney.
1890	Publication of the Draper Catalogue of Stellar Spectra.
1890, April 24	Spica announced by Vogel to be a spectroscopic binary.
1890, June	Gore’s Catalogue of computed Binaries.
1890, November	Study by Sir William and Lady Huggins of the spectra of Wolf and Rayet’s stars in Cygnus.
1890, November	Discovery by Barnard of a close nebulous companion to Merope in the Pleiades.
1890, November	McClean Spectrographs of the High and Low Sun.
1891	Capture-theory of comets developed by Callandreau, Tisserand, and Newton.
1891	Dunér’s spectroscopic researches on the sun’s rotation.
1891	Preponderance of Sirian stars in the Milky Way concluded by Pickering, Gill, and Kapteyn.
1891	Detection by Mrs. Fleming of spectral variations corresponding to light-changes in β Lyræ.
1891	Establishment of the Harvard College Station at Arequipa in Peru (height 8,000 feet).
1891	Variations of latitude investigated by Chandler.
1891	Prominence-photography set on foot by Hale at Chicago and Deslandres at Paris.
1891	Schmidt’s Theory of Refraction in the Sun.
1891, April	Meeting at Paris of the Permanent Committee for the Photographic Charting of the Heavens.
1891, May 9	Transit of Mercury.
1891, Aug. 19	Presidential Address by Huggins at the Cardiff Meeting of the British Association.
1891, Dec. 10	Nova Aurigæ photographed at Harvard College.
1891, Dec. 20	Photographic maximum of Nova Aurigæ.
1891, Dec. 22	First photographic discovery of a minor planet by Max Wolf at Heidelberg.
1892	Commencement of international photographic charting work.
1892	Photographic determination by Scheiner of 833 stars in the Hercules Cluster (M 13).
1892	Publication of Vogel’s spectrographic determinations for fifty-one stars.
1892	Publication of Pritchard’s photographic parallaxes.
1892, Jan. 2	Death of Sir George Airy.
1892, Jan. 21	Death of Professor Adams.
1892, Feb. 1	Announcement by Anderson of the outburst of a new star in Auriga.
1892, Feb. 5	Appearance of the largest sun-spot ever photographed at Greenwich.
1892, March	Photograph of Argo nebula taken by Gill in twelve hours.
1892, March 6	Discovery of a bright comet by Swift.
1892, June 29	Death of Admiral Mouchez. Succeeded by Tisserand as director of the National Observatory, Paris.
1892, Aug. 4	Favourable Opposition of Mars.
1892, Aug. 17	Rediscovery at Lick of Nova Aurigæ.
1892, Sept. 9	Discovery by Barnard of Jupiter’s inner satellite.
1892, Oct. 12	First photographic discovery of a comet by Barnard.
1892, Nov. 6	Discovery of Holmes’s comet.
1892, Nov. 23	Shower of Andromede meteors visible in America.
1892	Poynting’s Determination of the Earth’s Mean Density.
1892	Dunér’s Investigation of the System of Υ Cygni.
1892	Photographic investigation by Deslandres of the spectra of prominences.
1892	Photographs of the sun with faculæ and chromospheric surroundings taken by Hale with a single exposure.
1892	Investigation by T. J. J. See of the ancient colour of Sirius.
1892	Publication of T. J. J. See’s Thesis on the Evolution of Binary Systems.
1892	Chandler’s theory of Algol’s inequalities.
1892	Nebula in Cygnus photographically discovered by Max Wolf.
1893, Jan. 28	Kapteyn’s investigation of the structure of the universe.
1893, March 10	Gill announces his results from the Opposition of Victoria, among them a solar parallax = 8·809′.
1893, April 16	Total solar eclipse observed in South America and West Africa.
1893	Publication of Kruger’s Catalog der Farbigen Sterne.
1893	Conclusion of Boys’s series of Experiments on the Density of the Earth.
1893	Publication of Cordoba Durchmusterung, vol. i.
1893	Fabry shows comets to be dependents of the Solar System.
1893	Publication of Easton’s Voie Lactée.
1893	Campbell detects bright Hα in γ Argûs and Alcyone.
1893	Nova Normæ photographed July 10; discovered on plates, October 26.
1893, May 28	Death of Professor Pritchard.
1893, July 27	Installation of 28-inch refractor at the Royal Observatory, Greenwich.
1893, December	Exterior nebulosities of Pleiades photographed by Barnard.
1893, Dec. 6	Death of Rudolf Wolf.
1894, January	Sun-spot maximum.
1894	Publication of Potsdam Photometric Durchmusterung, part i.
1894	Publication of Roberts’s Celestial Photographs, vol. i.
1894	Wilson and Gray’s determination of the sun’s temperature.
1894	Barnard’s micrometric measures of asteroids.
1894	McClean’s gift of an astrophysical outfit to the Cape Observatory.
1894	Establishment of the Lowell Observatory at Flagstaff, Arizona.
1894	Taylor’s triple achromatic objective described.
1894, April 3	Discovery of Gale’s Comet.
1894	Sampson’s investigation of the sun’s rotation.
1894, Oct. 20	Favourable opposition of Mars.
1894, Nov. 11	Transit of Mercury.
1894, December	Howlett impugns the Wilsonian theory of sun-spots.
1894, Dec. 14	Death of A. Cowper Ranyard.
1895	Publication of Newcomb’s Astronomical Constants.
1895	Bailey’s Photometric Catalogue of 7,922 Southern Stars.
1895	Bailey’s photographic discovery of variable star clusters.
1895	Publication of E. W. Brown’s Lunar Theory.
1895	Tisserand’s theory of the inequalities of Algol.
1895	Stratonoff’s determination of the sun’s rotation from photographs of faculæ.
1895	Binary character of η Aquilæ spectroscopically recognised by Bélopolsky.
1895	Presentation of the Crossley reflector to the Lick Observatory.
1895, March 23	Great nebula in Ophiuchus discovered photographically by Barnard.
1895, March 25	Ramsay’s capture of Helium.
1895, April	Constitution of Saturn’s rings spectrographically demonstrated by Keeler.
1895	Binary character of δ Cephei spectroscopically detected by Bélopolsky.
1895, June 11	Death of Daniel Kirkwood.
1895, July 7	Death of F. W. G. Spörer.
1895, October	Nova Carinæ spectrographically discovered by Mrs. Fleming.
1895, Dec. 12	Nova Centauri spectrographically discovered by Mrs. Fleming.
1895, Dec. 28	Death of John Russell Hind.
1896	Gill’s Report on the Geodetic Survey of South Africa.
1896	Appearance of Loewy’s Photographic Atlas of the Moon, part i.
1896, January	Fessenden’s electrostatic theory of comets.
1896	Chandler’s Third Catalogue of Variable Stars.
1896	Publication of Lick Observatory Photographic Atlas of the Moon, part i.
1896, February	Effects of pressure on wave-length described by Humphreys and Mohler.
1896, April 5	Opening of new Scottish Royal Observatory on Blackford Hill, Edinburgh.
1896, April	Pickering’s photometric determinations of light curves of variable stars.
1896	One of the stars of Castor spectroscopically resolved into two by Bélopolsky.
1896, May	Third Astrographic Chart Conference at Paris.
1896, Aug. 9	Total eclipse of the sun visible in Novaya Zemlya. Reversing layer photographed by Shackleton.
1896, Aug. 30	Death of Hubert A. Newton.
1896, Sept. 18	Death of Hippolyte Fizeau.
1896, Oct. 20	Death of F. Tisserand. Succeeded by Maurice Loewy.
1896, Nov. 13	Detection by Schaeberle of Procyon’s missing satellite.
1896, Nov. 26	Death of Benjamin Apthorp Gould.
1896, November	Second series of hydrogen-lines discovered by Pickering in stellar spectra.
1896, December	Zeeman’s discovery of spectral modifications through magnetic influence.
1896, December	Oxygen-absorption identified in the sun by Runge and Paschen.
1896	Study of lunar formations by Loewy and Puiseux.
1896	Mounting of the Mills spectrograph at the Lick Observatory.
1897	Installation at Greenwich of the Thompson 26-inch photographic refractor.
1897	Publication of Miss Maury’s Discussion of the Photographed Spectra of 681 Stars.
1897	Callandreau’s researches on cometary disaggregation.
1897	Braun’s determination of the earth’s mean density.
1897	Tenuity of calcium vapour in chromosphere demonstrated spectroscopically by Sir William and Lady Huggins.
1897	Completion at the Cape Observatory of McClean’s spectrographic survey of the heavens.
1897	Twenty-one Wolf-Rayet stars found by Mrs. Fleming in Magellanic Cloud.
1897	Percival Lowell’s New Observations on the Planet Mercury presented to the American Academy.
1897, April 8	McClean recognises oxygen-absorption in helium stars.
1897, May 9	Death of E. J. Stone, Radcliffe Observer.
1897, June 10	Death of Alvan G. Clark.
1897, June 18	Spectrum of a meteor photographed at Arequipa.
1897, Oct. 21	Inauguration of the Yerkes Observatory.
1897	Rabourdin’s photographs of nebulæ with the Meudon reflector.
1897	Dr. See’s discoveries of Southern double stars with the Lowell 24-inch refractor.
1898, Jan. 22	Total eclipse of the sun visible in India.
1898, February	Binary character of ζ Geminorum ascertained spectroscopically by Bélopolsky.
1898	Star with proper motion of nearly 9′ discovered by Innes and Kapteyn from the Cape Durchmusterung plates.
1898, March 8	Nova Sagittarii photographed on Draper Memorial plates.
1898, June 20	Opening of Grand-ducal Observatory at Königsstuhl, Heidelberg.
1898	Keeler succeeds Holden as Director of the Lick Observatory.
1898	Bruno Peter’s results in stellar parallax.
1898	Lewis Swift’s discoveries of nebulæ at Echo California.
1898	Hale’s photographic investigation of carbon stars.
1898, Aug. 14	Discovery of Eros by Witt.
1898	Flint’s investigations of stellar parallax by meridian differences.
1898	Easton’s spiral theory of the Milky Way.
1898	Seeliger’s research on star distribution.
1898, October	Multiple hydrogen-bands observed by Campbell in Mira Ceti.
1898, November	Orbit of a Leonid meteor photographically determined by Elkin.
1899	Publication of Potsdam Photometric Durchmusterung, part ii.
1899	Innes’s Reference Catalogue of Southern Double Stars.
1899	Keeler’s photographs of nebulæ with the Crossley reflector and generalization of their spiral character.
1899, January	Spectrum of Andromeda nebula photographed by Scheiner.
1899, April	Photographic discovery of Nova Aquilæ by Mrs. Fleming.
1899, Aug. 26	Installation of 31-inch photographic refractor at Potsdam.
1899	Campbell’s detection of Polaris as spectroscopically triple.
1899, October	Duplicate discovery by Campbell and Newall of Capella as a spectroscopic binary.
1899, Nov. 15	Failure of the Leonids. Deflection of the stream predicted by Johnstone Stoney and Downing.
1899, December	Publication of Sir William and Lady Huggins’s Atlas of Representative Stellar Spectra.
1899	Thirty-two-inch photographic refractor mounted at Meudon.
1899	Issue of first volume of Potsdam measures of international catalogue plates.
1900, Jan. 27	Kapteyn’s determination of the apex of solar motion.
1900	Chase’s measures for parallax of swiftly-moving stars.
1900	Publication of Gill’s Researches on Stellar Parallax.
1900	Kapteyn proposes a method for a stellar parallax Durchmusterung, and gives specimen results for 248 stars.
1900	Burnham’s general catalogue of 1,290 double stars.
1900	Publication of the concluding volume of the Cape Photographic Durchmusterung.
1900, May 28	Spanish-American total eclipse of the sun.
1900, July	International Conference at Paris. Co-operation arranged of fifty-eight observatories in measures of Eros for solar parallax.
1900	Horizontal refractor, of 50 inches aperture, 197 feet focus, installed in Paris Exhibition.
1900, Aug. 12	Death of Professor Keeler. Succeeded by Campbell in direction of Lick Observatory.
1900, November	Opposition of Eros.
1900	Publication of Roberts’s Celestial Photographs, vol. ii.
1900	Complete publication of Langley’s researches on infra-red spectrum.
1900	Printing begun of Paris section of International Photographic Catalogue.
1901, Feb. 22	Nova Persei discovered by Anderson.
1901, February	Variability of Eros announced by Oppolzer.
1901, April 23	Apparition of a great comet at the Cape.
1901	Publication of Pickering’s Photometric Durchmusterung.
1901	Miss Cannon’s discussion of the spectra of 1,122 Southern stars.
1901	Kapteyn’s investigation of mean stellar parallax.
1901	Campbell’s determination of the sun’s velocity.
1901	Porter’s research on the solar motion in space.
1901	Bigelow’s magnetic theory of the solar corona.
1901	Hussey’s measurements of the Pulkowa double stars.
1901	Radial velocities of the components of δ Equulei measured at Lick.
1901, April 16	Death of Henry A. Rowland.
1901, June	Nebular spectrum derived from Nova Persei.
1901, Aug. 23	Nebula near Nova Persei photographed by Max Wolf.
1901, Sept. 20	The same exhibited in spiral form on a plate taken by Ritchey at the Yerkes Observatory.
1901, Nov. 8	Photograph taken by Perrine with the Crossley reflector showed nebula in course of rapid change.
1901, Sept. 19	Unveiling of the McClean “Victoria” telescope at the Royal Observatory, Cape of Good Hope.
1901	Sun-spot minimum.

TABLE II

CHEMICAL ELEMENTS IN THE SUN (ROWLAND, 1891).

Arranged according to the number of their representative Lines in the Solar Spectrum.

Iron (2000+).	Neodymium.	Cadmium.
Nickel.	Lanthanum.	Rhodium.
Titanium.	Yttrium.	Erbium.
Manganese.	Niobium.	Zinc.
Chromium.	Molybdenum.	Copper (2).
Cobalt.	Palladium.	Silver (2).
Carbon (200+).	Magnesium (20+).	Glucinum (2).
Vanadium.	Sodium (11).	Germanium.
Zirconium.	Silicon.	Tin.
Cerium.	Strontium.	Lead (1).
Calcium (75+).	Barium.	Potassium (1).
Scandium.	Aluminium (4).

TABLE III

EPOCHS OF SUN-SPOT MAXIMUM AND MINIMUM FROM 1610 TO 1901.

Minima.	Maxima.		Minima.	Maxima.		Minima.	Maxima.
1610·8	1615·5		1712·0	1718·2		1810·6	1816·4
1619·0	1626·0		1723·5	1727·5		1823·3	1829·9
1634·0	1639·5		1734·0	1738·7		1833·9	1837·2
1645·0	1649·0		1745·0	1750·3		1843·5	1848·1
1655·0	1660·0		1755·2	1761·5		1856·0	1860·1
1666·0	1675·0		1766·5	1769·7		1867·2	1870·6
1679·5	1685·0		1775·5	1778·4		1878·9	1884·0
1689·5	1693·0		1784·7	1788·1		1890·2	1894·0
1698·9	1705·5		1798·3	1804·2		1901·9

TABLE IV.

MOVEMENTS OF SUN AND STARS.

1. Translation of Solar System.

Apex of Movement.		Authority.	Date.
R. A.	Dec.
277° 30′	+ 35°	Newcomb	1898
273° 36′	+ 29° 30′	Kapteyn	1901
279°	+ 46°	Porter	1901
275°	+ 45°	Boss	1901
277° 30′	+ 20°	Campbell (from stellar spectroscopic measures)	1902
Velocity=12·4 miles per second (Campbell).

2. Stellar Velocities.

Name of Star.	Rate.	Direction.	Remarks.
	Miles per Sec.
δ Leporis	58	Receding	Campbell, 1901
η Cephei	54	Approaching	″ 1899
θ Canis Majoris	60	Receding	″ 1901
ι Pegasi	47	Approaching	″ ″
μ Sagittarii	47	Approaching	″ ″
ε Andromedæ	52	Approaching	″ ″
ζ Herculis	44	Approaching	Bélopolsky, 1893
61 Cygni	34	Approaching	″ ″
μ Cassiopeiæ	60	Approaching	Campbell, 1901
1830 Groombridge	59	Approaching	″ ″
Arcturus	4·3	Approaching	Keeler, 1890
Arcturus	278	Tangential	Accepting Elkin’s parallax of 0·024′
1830 Groombridge	150	Tangential	Parallax = 0·14′
μ Cassiopeiæ	113	Tangential	Parallax = 0·10′ (Peter)
Z. C. 5h 243	82	Tangential	Parallax = 0·312′ (Gill)
Lacaille, 2,957	78	Tangential	Parallax = 0·064′ (Gill)
Lacaille, 9,352	73	Tangential	Parallax = 0·283′ (Gill)
o2, Eridani	72	Tangential	Parallax = 0·166′ (Gill)
ε Eridani	61	Tangential	Parallax = 0·149′ (Gill)

TABLE V.

LIST OF GREAT TELESCOPES.

1. Reflectors—A. Metallic Specula.

Locality.	Aperture in Inches.	Focal Length in Feet.	Constructor.	Remarks.
Birr Castle, Parsonstown, Ireland	72	54	Third Earl of Rosse, 1845	Newtonian.
Melbourne Observatory	48	28	T. Grubb, 1870	Cassegrain.
Birr Castle	36	--	Third Earl of Rosse, 1839	Newtonian. Remounted equatoreally 1876.
Royal Observatory Greenwich	24	20	William Lassell, 1846	Newtonian. Presented by the Missess Lassell to the Royal Observatory
B. Silvered Glass Mirrors.
Ealing, near London	60	27	A. A. Common, 1891	Newtonian.
Yerkes Observatory	60	25	G. W. Richey, 1902	Can be employed at choice as a Coudé or a Cassegrain.
National Observatory, Paris	48	--	Martin, 1875	Newtonian. Remodelled for spectrographic work by Deslandres in 1892
Meudon Observatory	39	9·7
Lick Observatory	36	17·5	Calver, 1879	Mounted by Common at Ealing in 1879. Sold by him to Crossley, 1885. Presented by Crossley to the Lick Observatory, 1895.
Toulouse Observatory	32·5	16·2	Brothers Henry
Marseilles Observatory	31·5	--	Foucault
Royal Observatory, Greenwich	30	--		Cassegrain. Mounted as a counterpoise to the Thompson equatoreal.
Westgate-on-Sea	30	--	Common, 1889	The property of Sir Norman Lockyer.
Harvard College Observatory	28	--	H. Draper, 1870	Mounted for spectrographic work,1887.
Royal Observatory, Edinburgh	24	--	T. Grubb, 1872
Daramona, Ireland	24	10·5	Sir H. Grubb, 1881	Remounted 1891. Owned by Mr. W. E.Wilson.
Yerkes Observatory	23·5	7·7	Ritchey, 1901	Ritchey, Cassegrain, with an equivalent focal length of 38 feet.
Harvard College Observatory	20	--	Common, 1890
Crowborough, Sussex	20	8·2	Sir H. Grubb, 1885	Mounted with a 7-inch refractor.
2. Refractors.
Palais de l’Optique, Paris	49·2	197	Gautier, 1900	Mounted as a siderostat in connection with a plane mirror 79 inches across.
Yerkes Observatory	40	62	Alvan G. Clark, 1897
Lick Observatory	36	57·8	A. Clark and Sons, 1888	For photographic purposes a correcting lens is available, of 33 inches aperture, 47·8 feet focus.
Meudon Observatory	32·5	55·2	Henrys and Gautier, 1891	Mounted with a photographic refractor of 24·4 inches aperture.
Astrophysical Observatory, Potsdam	31·5	39·4	Steinheil and Repsold, 1899	Photographic. Mounted with a visual refractor 20 inches in aperture.
Bischoffsheim Observatory, Nice	30·3	52·6	Henrys and Gautier, 1886	Visual. Mounted on Mont Gros, 1,100 feet above sea level.
Imperial Observatory, Pulkowa	30	42	A. Clark and Sons, 1885	Visual. Mounted by Repshold.
National Observatory, Paris	28·9	--	Martin
Royal Observatory, Greenwich	28	28	Sir H. Grubb, 1894	Visual and photographic. Mounted by Ransome and Simms.
University Observatory, Vienna	27	34	Sir H. Grubb, 1881	Visual.
Royal Observatory, Greenwich	26	26	Sir H. Grubb, 1897	The Thompson photographic equatoreal.
Naval Observatory, Washington	26	29	A. Clark and Sons, 1873
Leander McCormick Observatory, Virginia	26	32·5	A. Clark and Sons, 1881
Cambridge University Observatory	25	--	T. Cooke and Sons. 1870	Presented to the University in 1889 by Mr. R. S. Newall.
Meudon Observatory	24·4	52·2	Henrys and Gautier, 1891	Photographic. Mounted with a visual 32·5-inch refractor.
Harvard College Observatory	24	11·3	A. Clark and Sons, 1893	Photographic doublet. The gift of Miss Bruce. Transfered in 1896 to Arequipa, Peru.
Royal Observatory, Cape of Good Hope	24	22·6	Sir H. Grubb, 1898	Photographic. The gift of Mr. McClean. Mounted with an 18-inch visual refractor.
Lowell Observatory, Flagstaff, Arizona	24	31	Alvan G. Clark, 1896	Visual. First mounted near the city of Mexico. Installed at Flagstaff, 1897.
National Observatory, Paris	23·6	59	Henrys and Gautier, 1891	Visual and photographic. Mounted as an equatoreal Coudé.
Halsted Observatory, Princeton, N.J.	23	32	A. Clark and Sons, 1883
City Observatory, Edinburgh	22	30	--	Mounted as a visual equatoreal on the Calton Hill, 1898.
Etna Observatory	21·8	--	Merz, 1897
Buckingham Observatory	21·2	--	Buckingham and Wragge
Porro Observatory, Turin	20·5	--	Porro
Chamberlin Observatory, Colorado	20	28	Alvan G. Clark and Saegmüller, 1894	Visual. Fitted with a reversible crown lens for photography.
Manila Observatory	20	--	Merz and Saegmüller, 1894	Visual. Provided with a photographic correcting lens.
Strasburg Observatory	19·2	23	Merz and Repsold, 1880
Brera Observatory, Milan	19·1	23	Merz and Repsold
Dearborn Observatory, Illinois	18·5	27	A. Clark and Sons, 1862	Mounted 1864
National Observatory, La Plata	18·1	29·5	Henrys and Gautier, 1890	Coudé Mount. Visual.
Lowell Observatory, Flagstaff, Arizona	18	26·3	Brashear, 1894	Mounted with a 12-inch Clark refractor as counterpoise.
Van der Zee Observatory, Buffalo, N.Y.	18	--	Fitz	Dismounted.
Bischoffsheim Observatory, Nice	16·5	26·2	Henrys and Gautier, 1889	Coudé Mount. Visual.
University Observatory, Vienna	16·5	29·5	Henrys and Gautier, 1890	Coudé Mount. Visual.
Jesuit Observatory, Zi-ka-Wei	16·5	22·5	Henrys and Gautier, 1897	Photographic. Mounted with a visual refractor of equal aperture.
Goodsell Observatory, Northfield, Minnesota	16·2	--	Brashear, 1891
Warner Observatory, Rochester, N.Y.	16	22	A. Clark and Sons, 1891
Grand-Ducal Observatory, Königsstuhl, Heidelberg	16	6·6	Brashear and Grubb, 1900	A twin photographic doublet. The gift of Miss Bruce. Mounted with a visual 10-inch refractor by Pauly.
Meudon Observatory	15·7	5·3
Washburn Observatory, Wisconsin	15·6	20·3	A. Clark and Sons, 1879
Teramo Observatory, Italy	15·5	--	T. Cooke and Sons, 1885	Formerly the property of Mr. Wigglesworth.
Royal Observatory, Edinburgh	15·1	--	T. Grubb, 1872	Presented by Lord Crawford.
Madrid Observatory	15	-	Merz
Tulse Hill Observatory	15	15	Sir H. Grubb, 1870	Lent by the Royal Society to Sir William Huggins. Mounted with an 18-inch Cassegrain reflector.
National Observatory, Paris	15	29	Lerebours
Harvard College Observatory	15	22	Merz, 1847
National Observatory, Rio de Janeiro	15	--
Tacubaya Observatory, Mexico	15	15	Sir H. Grubb, 1880
Stonyhurst College Observatory	15	15	Sir H. Grubb, 1893
Brera Observatory, Milan	15	--
University of Mississippi	15	15	Sir H. Grubb, 1893	Visual. Mounted with a photographic 9-inch refractor.
Imperial Observatory, Pulkowa	15	22·5	Merz and Mahler, 1840
Maidenhead Observatory	15	--	Sir H. Grubb, 1893	The property of Mr. Dunn. Mounted with a twin photographic refractor.
Odessa Observatory	14·9	--	Merz, 1881
Bischoffsheim Observatory, Nice	14·9	23	Henrys and Gautier
Brussels Observatory	14·9	20	Merz and Cooke, 1877
Observatory of Bordeaux	14·9	22·4	Merz and Gautier, 1880
Observatory of Lisbon	14·9	--	Merz and Mahler

TABLE VI.

List of Observatories employed in the Construction of the Photographic Chart and Catalogue of the Heavens.

All are provided with 13-inch photographic, coupled with 11-inch visual refractors:

Name of Observatory.	Constructors of Instruments.
	Optical Part.	Mechanical Part.
Paris	Henrys	Gautier
Algiers	,,	,,
Bordeaux	,,	,,
San Fernando (Spain)	,,	,,
Vatican	,,	,,
Cordoba	,,	,,
Montevideo	,,	,,
Perth, Western Australia	,,	,,
Helsingfors	,,	Repsold
Potsdam	Steinheil	,,
Catania	,,	Salmoiraghi
Greenwich	Sir H. Grubb	Sir H. Grubb
Oxford	,,	,,
The Cape	,,	,,
Melbourne	,,	,,
Sydney	,,	,,
Tacubaya (Mexico)	,,	,,

Footnotes:

1630 Comptes Rendus, t. xliv., p. 339.

1631 A. A. Common, Memoirs R. Astr. Soc., vol. i., p. 118.

1632 Newcomb, Pop. Astr., p. 137.

1633 Month. Not., vol. liv., p. 67.

1634 Keeler, Publ. Astr. Pac. Soc., vol. ii., p. 160.

1635 H. Grubb, Trans. Roy. Dub. Soc., vol. i. (new ser.), p. 2.

1636 Hale, nevertheless (Astroph. Jour., vol. v., p. 128), considers that refractors preserve their superiority of visual light-grasp over Newtonian reflectors up to an aperture of 52-1/2, while equalisation is reached for the photographic rays at 34 inches.

1637 Astroph. Jour., vol. v., p. 130.

1638 Phil. Trans., vol. cxlviii., p. 465.

1639 Optics, p. 107 (2nd ed., 1719).

1640 Observatory, vol. viii., p. 85.

1641 Holden on Celestial Photography, Overland Monthly, Nov., 1886.

1642 Observatory, vol. xv., p. 283.

1643 Bailey, Astroph. Jour., vol. x., p. 255.

1644 Harvard Circulars, Nos. 2, 18, 24, 33;

1645 Loewy, Bull. Astr., t. i., p. 286; Nature, vol. xxix., p. 36.

1646 Nature, vol. xxiv., p. 389.

1647 Ibid., vol. xxix., p. 470.

1648 Trans. R. Dublin Soc., vol. iii., p. 61.

1649 Observatory, vol. vii., p. 167.

1650 Loewy, Bull. Astr., t. i., p. 265.

1651 Phil. Trans., vol. clxxi., p. 653.

1652 Janssen, L’Astronomie, t. ii., p. 121.

1653 Rev. A. L. Cortie, Astr. and Astrophysics, vol. xi., p. 400.

1654 Phil. Mag., vol. xiii., 1882, p. 469.

1655 Bull. Astr., t. iii., p. 331.