' 
336 JOHN TEBBUTT. 
Swift's Comet (I.) 1892. 
This comet was discovered as a bright object on March 7, 1892 
by L. Swift at the Warner Observatory, Rochester, New York, and 
the news of its discovery was cabled from Kiel to the Australian 
Colonies, the notification reaching me on the evening of the 9th. 
The sky was cloudy on the following morning, and it was not till 
the morning of the 11th that I succeeded in finding the stranger. 
From that date to April 23 inclusive, an excellent series of filar 
micrometer measures in a bright field were obtained with the eight 
inch equatorial. All the subsequent observations were made with 
a square bar-micrometer in a dark field on the four and a half 
inch instrument. After May 2 the comet was too far north, but 
its observation was continued by northern observatories. The 
differential co-ordinates resting on the single comparisons of March 
10 and April 9 were obtained by observing the instant when the 
comet and comparison star were together bisected by the transit 
or one of the declination threads of the micrometer. As a suffici- 
ently exact ephemeris is not available for the calculation of the 
reductions to the earth’s centre the usual parallax factors log. § 
log. 5 are furnished instead. p and q denote the reductions to the 
earth’s centre in time and arc respectively, and P the comet’s 
equatorial horizontal parallax. There are as yet no very decisive 
signs of elliptic motion in this comet. Herr Berberich of Berlin 
finds that observations extending over a period of four months 
can be satisfied by an ellipse with a period of 20000 years. The | 
comet was visible to the naked eye from the time of its discovery 
till it ceased to be observed at Windsor. It passed its perihelion 
on April 7, 1892. 
Winnecke’s Periodical Comet, 1892. 
It will perhaps be within the recollection of the members of the 
Royal Society that this comet was observed at its last return which 
took place in 1886. A paper containing the Windsor observations 
of that year was read before the Society in September 1887 and 
published in their Journal, Vol. xx1., p. 159. It will be unneces- 
sary to repeat the history of this interesting comet previously to. Z 
