159 

 RESULTS OF OBSERVATIONS OF COMETS VI. AND 

 VIL, 1886, AT WINDSOR, N.S.W. 



By John Tebbutt, F.R.A.S., &c. 



[Read before the Royal Society of N.S.W., September 7, 1887.'] 



Ix December, 1886, I communicated to the Royal Society my 

 observations of Comets Fabry, Barnard, and Brooks, and they 

 were duly published in the Society's Journal and Proceedings for 

 that year. In addition to these comets two others were observed 

 •during the year, which have proved of unusual interest to 

 astronomers. These are Comets VI. and VII., 1886. 



Comet VI., 1886. 

 A telescopic comet was discovered by the indefatigable Pons on 

 June 12, 1819, which turned out to be a remarkable one, inasmuch 

 as it was shown by Professor Encke to be moving in an elliptic 

 orbit with a period a little exceeding 5^ years. Notwithstanding 

 the shortness of the assigned period 39 years elapsed before the 

 comet was again seen. On March 8, 1858, Dr. Winneckeat Bonn 

 discovered a small comet which was at first regarded as a new one, 

 but on calculating the elements of its orbit he made the further 

 pleasing discovery that the object was identical with that detected 

 by Pons in 1819. The comet was not seen at its next return to 

 perihelion, but in the Astronomische Nachrichten of February 11, 

 1869, O. Linsser of Pulkowa published a sweeping ephemeris based 

 on elements derived from the appearance of 1858. On April 9, 

 he issued an extended ephemeris which enabled Dr. Winnecke to 

 rediscover the comet on the date of publication. At this appearance 

 it was well observed at several stations. In the above periodical 

 for November 23, 1874, Dr. Oppolzer of Vienna, published the 

 result of an investigation of the orbit from the series of observations 

 in 1858 and 1869 and also an accurate ephemeris for January and 

 February, 1875. In this investigation he carefully accounted for 

 the perturbations of the comet's movements due to the action of the 

 large planets Jupiter and Saturn. With the help of this ephemeris 

 M. Borelly, at Marseilles, detected the comet on February 1, and 

 the interesting visitor was again well observed. The errors of the 

 ephemeris did not exceed sixteen seconds of time in right ascension 

 and one minute in declination The comet itself was faint and 

 diffused. It was not seen at the next return, but in the Astrono- 

 mische Nachrichten of March 30, 1886, appeared an approximate 

 ephemeris by Dr. Lamp, of the Royal Observatory at Kiel, 

 calculated on three assumptions of the time of perihelion passage, 

 namely, August 27, 31, and September 4, 1886. This ephemeris 

 extended to the close of June, 1886, but the comet not having 

 been discovered in consequence probably of its great distance from 

 the sun and earth, another ephemeris was published by the same 

 astronomer extending to the middle of September last. Meanwhile 



