RESULTS OF OBSERVATIONS OF COMETS I. AND II. 



285 



very distinctly seen in strong twilight with the 8 inch telescope 

 and a magnifying power of 74 diameters, and comparisons could 

 therefore be made on these occasions without artificial illumination 

 of the micrometer-threads. The comparisons were continued until 

 the comet was extinguished in the increasing twilight. 



The following table containing the approximate sidereal times 

 of the comet's last comparison-transit and of sunrise on each 

 morning at the close of the series will convey some impression of 

 the brightness of the comet in twilight : — 



Astronomical Date. 



Sidereal Time of 



Interval. 









Last Comparison. 



Sunrise. 







h. m. 



h. m. 



m. 



March 19 



17 33 



17 56 



23 



21 



17 37 



18 5 



28 



25 



18 5 



18 24 



19 



28 



18 13 



18 38 



25 



29 



18 20 



18 42 



22 



31 



18 28 



18 52 



24 



April 1 



18 33 



18 57 



24 



2 



18 33 



19 2 



29 



There was very thin cloud on March 19th and 29th. The 

 Windsor positions extend from February 28th to April 3rd. After 

 the last mentioned date clouds or fog prevented observation for 

 several mornings until the comet at length got too far north to be 

 followed. All the positions depend on a filar-micrometer with a 

 single position and two distance-threads. The micrometer was so 

 adjusted that the position-thread was coincident with a meridian 

 of right ascension and the distance-threads were parallel to the 

 equator. In each comparison, therefore, a single transit was 

 observed for difference of right ascension. The instrumental 

 differences are all corrected for refraction, which correction 

 amounts in no case to a second of arc. The earlier observations 

 of March 7th and 14th were made with the 4 J inch, and all the 

 other observations with the 8 inch-equatorial. One authority 

 only, and that a good one, has been selected for the mean place 

 of each comparison-star. The usual reductions from the mean to 

 the apparent places, and likewise the logarithmic factors for the 

 reduction of the comet's observed places to the centre of the earth 

 are added. P denotes the comet's equatorial horizontal parallax 

 in seconds of arc, and p and q the reductions in seconds of time 

 and arc respectively. The observations fully reduced have long 

 since been forwarded to Europe in three instalments. The first 

 instalment, which was published in the Astronomische JSfachrichten 

 of April 16th, turned out exceedingly useful for a provisional 

 determination of the elliptic elements of the comet's orbit by Herr 

 A. Berberich, of the Recheninstitut, Berlin. The position 



