542 



NA TURE 



[August i, 1901 



The observations show that the length of the period of 

 variability, reckoning from maximum to maximum, began after 

 March 27 to increase from tlvce days iofour days. 



The two following maxima, after that of April 8, occurred on 

 the 13th and l8th, so that the period became still more 

 lengthened, namely to about five days. Further observations 



The curve is drawn to satisfy as far as possible all the obser- 

 vations made at Kensington. The dotted portions represent the 

 possible light-curve for those times when no estimates for magni- 

 tude could be secured. 



In the plates the abscissae represent the time element and the 

 ordinates that of magnitude. 



up to May 5 seem to indicate that the five-day period is 

 shortening. 



Another interesting observed fact was that the light of the 

 Nova at the minimum on the 25th was more intense than at the 

 preceding minimum on the 21st, the estimated difference of 

 . magnitude at these times being about 4-tenths of a magnitude. 



Colour. —In the first part of the period covered by the later 

 observations, the colour of the Nova has been generally de- 

 scribed as yellowish-red, red with a yellow tinge and yellow with 

 a reddish tinge. Since April 25 the colour has been perhaps 

 more red than formerly and sometimes noted as very red. 



It is interesting to remark that the colour varies periodically 



Unfortunately the increasing twilight and theunfavourable position 

 of the Nova make it very difficult now to determine the magni- 

 tudes correctly. 



The two plates accompanying this paper illustrate graphically 

 the various fluctuations of the light of the Nova from February 

 22, when it had not quite attained its maximum brilliancy, to 

 May 5. 



NO. 1657, VOL. 64] 



with the change in magnitude. At maximum it is 01 a distinct 

 yellowish-red hue, but at or near minimum the yellowish tinge 

 disappears and the Nova appears very red. 



T/ie Visual Speitrivn. — In the continued observations the C 

 and F lines of hydrogen have always been recorded as " con- 

 .•-picuous," other prominent lines being near \ 447, X 465 and 

 A 501 (the last named being sometimes as bright as F or even 



