185 
The maxima give the period =277 days, and the minima 
=275. The mean period is therefore about 276 days. 
The highest observed magnitude at maximum is 8*7. 
At minimum the star falls below 13*5 magnitude. 
U Bootis. 
1855-0. a = 14h. 47m. 37*4s. a=+18°17T'. 
This variable is more regular in its changes than either 
U Canis minoris or Y Geminorum, and its period much 
shorter. The observed maxima and minima are as follows:— 
Maxima : 
1880, March 22. 
„ September 15. 
1881, August 31. 
Minima : 
1880, June 11. 
1881, May 31. 
It was equal to 11*5 magnitude when decreasing. 
1880, May 5. 
„ October 29. 
1881, April 23. 
„ October 14. 
And equal to 11 '5 magnitude when increasing. 
1880, July 22. 
1881, July 4. 
The mean period derived from the above data is 175*5 
days ; and the mean interval from minimum to maximum 
is 94-0 days; and from maximum to minimum 81*5 days. 
A maximum may be expected to occur about August 17, 
1882. 
The highest observed magnitude at maximum is 9*15, 
and the lowest at minimum 13-6, the extreme range of 
variation being therefore 4*45 magnitude. 
