404 



Mr. J. N. Lockyer. On the Cause of [Nov. 21, 



drawn entirely within the orbit of the secondary body. I gave tables 

 to show that these tests were satisfied by all the variables included 

 in Duner's catalogue of red stars.* In the tables which follow, it 

 will be seen that by far the greater number of variables in the group 

 under discussion fall in species 9 and 10, which may fairly be taken 

 to represent the mean condensation, there being in all 15 species. 

 There can, therefore, be no doubt that the three tests just referred to 

 are fully satisfied. 



In this paper I propose to further test my theory by the colour 

 observations of Chandler and by the question of irregularity, con- 

 fining myself to stars known to belong to Group II of which Chandler 

 gives the degree of redness. The stars selected for discussion are 

 the Ilia variables from Gore's revised catalogue. 



II. Details of Vaeiables of Geoup II. 



The following tables contain all the particulars of stars with 

 periods varying from 50 to 500 days. Gore's, Chandler's, and 

 Duner's star numbers are given as well as the star's name. The 

 magnitudes of the variable at maximum and minimum, and also the 

 period, have been taken from Gore. 



Colour Notation. 



On Chandler's colour scale corresponds to pure white, 1 to white 

 very slightly tinged with yellow, 2 and 3 to deeper yellow tinges, 

 4 to orange, 5, 6, 7, 8 and 9 to gradually deepening reds, and finally 

 10 corresponds to the deepest red stars known, such as II Leporis. 



The colour notation employed by Duner is as follows : — 



Rrrj Almost absolute red. 



Rrj Red-yellow fonce. 



Rj Red-yellow. 



Jr Yellow-red. 



Jjr Clear yellow-red. 



In the Bakerian Lecture for 1888 I gave a series of tables in which 

 the stars of Group II were classed in different species according 

 to their spectra. I have accordingly given with each variable 

 the number expressing the species to which it belongs. In some 

 cases, the details have not been sufficient to assign the star to a 

 definite species, but have been enough to determine whether it was 

 near the first (Species 1) or the last (Species 15). In such cases, the 

 words " early " or "late" are appended. Where the species of a 

 star is doubtful, the word " indeterminate " expresses that fact. 



* ' Les Etoiles a Spectres de la troisieme Classe.' (Stockholm, 1884.) 



