( *i79 ) 



the major axis at right angles to the line of the nodes. In this 

 waj we find : 



a=1.7209; }t==:0.5015; ;=0.2276; q=lMU; i'=7\2b; e—OM; tü=zl80«. 



In the next tables the columns d and C^ show the light-grades 

 computed by means of the first five elements, neglecting the excen- 

 tricitj. The columns C\ and C^ contain the same quantities taking 

 into account the excentricity. 



The mean deviation of the values in the columns Oj — C/ and 

 0, — Cy is ± 0.17 light-grades, whereas Argelander assigns the value 

 ±0.16 to the mean error of the ordinates of his light-curve (prob. 

 error 0.1095). It would be quite illusory therefore to endeavour to 

 obtain an improved agreement. Against the elliptic orbit there is 

 however the grave objection that it gives the first maximum 0.18 

 days after — , the second maximum 0.10 days before the corresponding 

 maxima of Argelander's light-curve. In the circular orbit the first 

 maximum lies only 0.02 days, the second 0.06 days later, whereas 

 the agreement is still very satisfactory. 



14. Finally we communicate a set of circular elements obtained 

 by a repeated approximation from the light-curve of Dr. Pannekoek : 



a — 1.5378 ; x == 0.5378 ; / = 0.2900 ; q — 1.4609. 



In deriving them we assumed that a cannot fall short of 1 -|- ;«. 

 We further assumed the theoretical principal minimum to coincide 

 with the observed minimum. 



In the following table t is the number of hours before and after 

 the theoretical principal and secondary minimum; 0^ and 0^ are 

 the light-grades at the same moments, as read off from Dr. P.'s 

 light-curve; Cj and C^ the light-grades of the theoretical curve. 



The results have been graphically represented in Fig. II. The 

 remaining deviations are mainly positive before the first minimum ; 

 after that they are negative. At the secondary minimum the signs 

 are reversed. The deviations might be rather considerably diminished 

 if, with a small excentricity {e sin to =: O.OJ 6), we place the principal 

 minimum in Dr. Pannekoek's light-curve 0.063 days later, the 

 secondary minimum 0.069 earlier. In this way, however, the interval 

 in lime min. I — min, II is diminished more considerably than 

 seems admissible. 



For the rest it need not be said, that in the present case, where 

 two gaseous bodies seem to be in contact, the Keplerian equations 

 of motion must give only a rough approximation, while the action 

 of the tides must contribute its part to mask the influence of the 



