The Variable Star Algol. 347 
different places; thus affording a means of learning the real 
errors of observation. Since the autumn of Jast year I have 
collected 8 minima, which have been determined by several ob- 
“servers, the number of the several observations amounting to 33, 
From these 33 observations the probable uncertainty in the de- 
termination of a minimum by a single observer is deduced as 
5-625, But during the same time there were, besides these, 9 
other minima obtained froma single observer. These observa- 
tions, 42 in all, I have, in order to be more independent of the 
length of the period, combined in two means, compared the sev- 
eral observations singly with these, and thus found the probable 
etror of such an observation to be 5™-895. ‘This error is some- 
what larger than the preceding; still the difference lies consider- 
ably within the limits of uncertainty of both determinations, 
and consequently cannot warrant us in inferring that the period 
18 subject to irregular variations, but merely that, if such exist, 
they can only be extremely small. The assumption of such an 
itregularity, amounting to but little more than 1", would bring 
the two numbers into perfect agreement. 
0 make the agreement in the several results more clear, I will 
here give the 24 minima observed during this autumn and win- 
ter, after reducing them by assuming the period 24 20h 48™ 53, 
to one principal epoch, namely, the minimum of Oct. 8. The 
atinexed table contains in the first column the number of pe- 
tiods elapsed since 1800, Jan. 2 ;—the second, the time as ob- 
; Minima of Algol. 
No. minimum] —O 
pe em. } bserved Paris time. Observer. |Equation cali idl Reduced time. 
A we he m. s. | h. m. s. 
6959 Aug, 20 1128 27 A. +027 | Oct.8 51955 
11 30 27 $d. 21 55 
6966 Sept. 9 1323 1 B. +259 34 50 
Jo 25.-3 K. < 86 62 
6967 Sept.12 965334 | B +3 20. 16 51 
10_ 2 93 Sd. 25 40 
1015 9 A. 38 26 
10 16 54 Oo. 40 11 
Sept. 29 14 53 52 B. +511 25 42 
Oct. 2 1143 45 K. +527 26 58 
1146 3 A. 29 16 
1146 4 B. 99 17 
11.58 19 M. 41 25 
12 044 0. 43 57 
127° 18% Sd. 45 65 
Oct. 23 1318 28 Sd. + 6 55 20 58 
Oct. 28° 7 157 A. +712 26 58 
7 739 K. 82 40 
71130 H. 86 31 
71848 N. 43 49 
Nov.14 11 51 46 B. -+-'7 35 23 52 
) 7 101981 A. +7 2 20 0 
10 23 10 Sd. 23 39 
10 25 31 K. Oct.8 526 0 
