January 6, 1899.] 



SCIENCE. 



9 



great 26- inch eqtatorial refractor by Alvan 

 Clark & Sons, which was then the largest 

 telescope in the world. 



A continuous series of Sun, Moon and 

 planet meridian observations was carried 

 on from 1861 to 1865 with the mural circle 

 and the transit instrument. In the begin- 

 ning of 1866 the new Pistor and Martins 

 meridian circle was put in service, and ob- 

 servations were made with it in the old 

 west transit room until 1869, June 5. It 

 was then removed to the new transit room, 

 where it was used from February 2 to 

 August 15, 1870, when observations were 

 suspended for some repairs on the instru- 

 ment. They were resumed in 1871, August 

 1, and then continued until 1891, June 28, 

 when the instrument was dismounted for 

 removal to the new Observatorj'. In con- 

 nection with the Sun, Moon and planet ob- 

 servations, there were made on this instru- 

 ment extensive determinations of the posi- 

 tions of the Ephemeris stars and of large 

 numbers of miscellaneous stars. When the 

 mural circle and transit instrument were 

 relieved of the planet work. Professor Yar- 

 nall devoted them to the completion of the 

 determination of the positions of all miscel- 

 laneous stars which had been observed with 

 them since 1845. These collected observa- 

 tions form Yarnall's catalogue, which was 

 published later. The equatorials were as- 

 siduously employed on the observation of 

 asteroids, comets, occultations, double stars, 

 satellites, and other work for which they 

 were especially adapted. 



The annual volumes of observations were 

 published regularly from 1861 to 1890, and 

 the principal memoirs and researches of 

 greater or less extent appearing in them 

 during this period are as follows : 



The solar parallax ; from equatorial observations 

 of Mars, 8.8415" by Professor Hall, Washington Ob- 

 servatory 1863, p. XI ; from meridian observations 

 of Mars, 8.83 lu" by Assistant Astronomer Ferguson, 

 Washington Observations, 1863, p. XI. 



Discussion of the solar parallax by all known 

 methods, 8.848" by Professor Newcomb, Washington 

 Observations, 1865, App. II. 



A catalogue of the positions of 151 stars in Prtesepe 

 by Professor Hall, Washington Observations, 1867, 

 App. IV. 



Reports on the solar eclipse of 1869, August 7 

 Washington Observations, 1867, App. I. 



Reports on the solar eclipse of 1870, December 22 

 Washington Observations, 1869, App. I. 



Reports on the solar eclipse of 1873, July 29 

 Washington Observations, 1876, App. III. 



Reports on the solar eclipse of 1880, January 11 

 Washington Observations, 1876, App III. 



The following embrace all of Hall's double-star 

 work with the 26-inch equatorial ; Washington Ob- 

 servations, 1876, App IV., and Washington Observa- 

 tions, 1888, App. I. 



The time of rotation of Saturn on its axis was de- 

 termined by Professor Hall by means of an equatorial 

 spot which was visible from 1876, December 7, to 

 1877, January 2. The period deduced was 10''14"" 

 23.8^^ mean solar time. The paper may be found in 

 the Astronomische Naolirichien No. 2146. 



On the right ascensions of the equatorial funda- 

 mental stars, by Professor Newcomb, Washington 

 Observations, 1870, App. III. 



Researches on the motion of the Moon, by Professor 

 Newcomb, Washington Observations, 1875, App. II. 



The Uranian and Neptunian systems, Professor 

 Newcomb, Washington Observations, 1873, App. I. 



The central parts of the nebula of Orion, Professor 

 Hoklen, Washington Observations, 1878, App. I. 



A catalogue of 10,964 stars from observations on 

 the mural circle and transit instrument, by Professor 

 Yarnall, revised edition by Professor Frisby, AVash- 

 ington Observations, 1884, Ai)p. I. 



A catalogue of 1963 stars observed by Gilliss, at 

 Santiago, Chili, edited by Professor Harkness, 1868, 

 App. I. 



Observations and orbits of the satellites of Mars, 

 Washington 1878. This memoir is bound with some 

 copies of Washington Observations, 1875. 



The two satellites of Mars were discovered by 

 Professor Hall in August, 1877, with the 26-inch 

 equatorial. 



The six inner satellites of Saturn, by Professor 

 Hall, Washington Observations, 1883, App. I. 



Saturn and its rings, by Professor Hall, Washington 

 Observations, 1885, App. I. 



Observations for stellar parallax, by Professor Hall, 

 Washington Observations, 1883, App. II. 



The solar parallax and its related constants, by 

 Professor Harkness, Washington Observations, 1885, 

 App. III. 



