40 REPORT — 1859. 



short period of 97 days was detected at the Radcliffe Observatory, at its very next 

 return, in March 1850. The star is visible only for about ten or twelve clays. To 

 what an infinity of faintness it must diminish during its 85 days of invisibility is 

 beyond all conception, and perfectly overwhelming to the imagination ! Its appear- 

 ances show a pretty regular periodicity ; but here again it is strangely anomalous, for 

 it sometimes fails to return at all, as will shortly appear from the projection. The 

 colour is invariably bluish white, and at some maxima its light is ever dancing and 

 unsteady ; at others exactly the reverse, as pale and calm as a planet's. Requesting 

 attention to the diagram so freely striped with red* lines, the upper limit no longer 

 represents the 6th but the 7*5 magnitude ; the lowest line, the 15th — a trifle beyond 

 the vanishing-point of the large reflector of Mr. Worthington, of Manchester ; 

 which has been directed to it frequently, and to excellent purpose, by my friend 

 Mr. Baxendell, of that city. 



At its discovery by Mr. Hind, on 1855, December 15, it was estimated of the 

 9th magnitude, and was announced in the Times as " a new planet at its stationary 

 point, or a new variable star." On December 18 it was a little fainter, though still 

 visible, but disappeared before the end of the month. The black hyperbolic-looking 

 curve, shaped agreeably to later re- appearances, but fitted in to Mr. Hind's dates, 

 shows the probable nature of its changes at its first recognition. The red lines fol- 

 lowing are records of invisibility, showing that the star was looked for but not seen, 

 and therefore less than the magnitude indicated by the top of each such red line. 

 Thus, on 1858, May 16, an unfavourable night at Manchester, stars of the 13'4 

 magnitude were just visible when U Geminorum was not. On 1856, January 12, 

 a fine night, it was invisible to Mr. Hind with the South Villa equatorial, and there- 

 fore less than 13'5 magnitude. On Jannary 27, when sought for at Oxford, with a 

 small but excellent portable telescope, 2\ inches in aperture, it was invisible, and 

 under the 11th magnitude. As previously stated, its period was detected at its 

 first return, at the Radcliffe Observatory, when three observations were obtained. 

 It must have passed its maximum on 1856, March 23. It was seen of the 9'6 mag- 

 nitude on the 26th ; of the 10*2 magnitude on the 27th ; of the 11th magnitude on 

 the 29th, but had quite disappeared on April 2, and was then less than the 13'5 

 magnitude. Several records of invisibility follow up to the middle of June, when 

 the star not being circumpolar was lost sight of at its conjunction with the sun. 

 From May till September it is not observable from this cause. The maxima due on 

 June 25 and September 30 were thus lost. The next, on 1857, January 5, was also 

 lost, owing to the prevalence of cloudy weather from December 29 to January 14. 

 The records of invisibility are, however, pretty numerous about this time, and prove 

 it was well looked after. The maximum of 1S57, April 9, was well observed, the 

 star being seen twice before, and five times after the turning-point by me ; and once 

 on April 13, as a 10 - 3 magnitude, by Mr. Baxendell, on a night when I had no 

 observation. It is gratifying to find the independent comparisons of two observers 

 — different eyes and telescopes — thus perfectly agreeing with the same unbroken 

 light curve. U Geminorum was again lost in the summer months at its conjunction, 

 and therefore the maximum due on July 18 escaped observation. On October 30 

 the variable was visible, but only of the 9'7 magnitude, and as it was invisible and 

 under the 12 - 3 magnitude on October 27, when already five days past due, it is pro- 

 bable that it did not surpass the observed magnitude at that maximum. 



An important stage of its history is now at hand. It was being sought for at 

 Oxford, and also at Manchester, and though due on 1858, January 27, was not 

 seen. If it appeared at all, which is doubtful, it could not exceed the 11th magnitude. 

 But at the next due apparition, May 4, it positively did not come at all ; for Mr. 

 Baxendell was searching night after night, with his great reflector, and limited 

 it "under 1 4 -J- magnitude," as shown by the short red (dotted) lines represent- 

 ing his valuable records, at the very time it was due at a maximum. The August 

 apparition occurred in conjunction, and the star was justly supposed to have " ex- 

 pired" or died out gradually. But on November 16 it returned, nearly as bright 

 as ever, as shown by the combined observations made at Oxford and Manchester. 

 And lastly, on February 19, 1859, it acquired a maximum equal to any previous 



* The red lines in the original diagram are represented by dotted lines. (See Plate I.) 



