123 
by the method of least squares, I obtained the following 
results : — 
1859, Oct. 27, to 1861, Oct. 8, nine minima gave the 
mean period = 70*88 days. 
1861, Oct. 8, to 1864, Aug. 30, nine minima =70*46. 
1864. Aug. 30, to 1866, Dec. 22, nine minima = 70.44. 
1866, Dec. 22, to 1868, Sep. 12, five minima =69.96. 
The interval from 1868, Sep. 12, to 1878, Aug. 19, was 
3628 days, and comprised 52 periods : the mean period was 
= 69*77 days. 1878, Aug. 19, to 1879, Dec. 24, six minima 
treated by the method of least squares gave the mean 
period = 70*00 days. 
These results show that the period had a minimum value 
in the long interval from 1868, Sep. 12, to 1878, Aug. 19, 
and that it has since slightly increased ; but as it might be 
doubted whether an error of one period might not be made 
in estimating the number of periods in so long an interval 
it may be stated that if it be assumed that only 51 periods 
elapsed during the interval the mean period would be 71*13 
days, whilst 53 periods in the interval would give a mean 
of 68*45 days ; but looking to the results for the nine years 
1859-1868, and the two years 1878-9, it is evident that a 
mean period of 71*13 days is too long, and one of 68*45 days 
too short to be admissible. 
The secondary minima I have observed from the discovery 
of the star’s variability to the end of 1879 are as follows : — ■ 
No. 
Date, 
Mag. 
Days 
in 
Interval. 
Number 
of 
Periods. 
1. 
1859, Nov. 25.... 
.. 8*6 
2. 
1860, June 23 
.. 8*7 
211 
3 
3. 
„ Sep. 10 — 
.. 9*1 
79 
1 
4. 
1861, June 24 
.. 8*8 
287 
4 
5. 
„ Aug. 30.... 
.. 9*1 
67 
1 
6. 
„ Nov, 11.... 
.. 9*2 
73 
1 
7. 
1862, Aug. 18 
.. 9*1 
280 
4 
8. 
„ Oct. 28...,, 
.. 9*3 
71 
1 
