1889.] Variability in condensing Sivarms of Meteorites. 



409 



III. The Relation op Coloue to Period. 



Mr. Chandler's Observations. 



In the tables given the particulars relating to period and range of 

 variability are taken from Gore, and Chandler's colour-numbers are 

 placed in a separate column. 



Mr. Chandler has shown* that there is an intimate connexion 

 between the length of period of a variable star and its colour. In 

 general, the longer the period the redder the tint. If the period is 

 between 500 and 600 days, the mean redness on his scale is about 

 7'5 ; for periods of about 300 days, it is about 3 ; and for shorter 

 periods it is 1 or 2. This is exactly what would happen if my theory 

 were true. 



In order to investigate the cause of this relation it is necessary that 

 I should refer to Chandler's work in connexion with my previous 

 classification of the 297 bodies of Group II spectroscopically observed 

 by Duner. 



The Relation of Colour to the Degree of Condensation in Swarms of 



Group II. 



In the Bakerian Lecture I provisionally divided the bodies of 

 Group II into fifteen species, the first being the least and the last the 

 most condensed swarms. If then the degree of condensation of a 

 swarm has any relation to colour, the work of Chandler on the colours 

 of variable stars, taken in conjunction with this classification, ought to 

 enable us to determine the nature of such relation. 



In order to determine Chandler's colour-numbers corresponding to 

 these, tables were prepared comparing Duner' s colours of the variable 

 stars of the group with the colours assigned by Chandler to the same 

 stars. Two stars which Duner gives as Rrrj occur in Chandler's list, 

 the colours being 6*9 and 8*1 respectively, or a mean of 7'5. 



The colour-number corresponding to Rrrj has therefore been taken 

 as 7*5. Similarly, there are ten Rrj stars in Duner's list for which 

 the mean colour-number assigned by Chandler is 5"9, and so on. 



Duner's Colour = Rrrj. 



No. (Duner). 

 92 

 106 



Colour (Chandler). 

 6-9 

 8-1 

 Mean 7 '5. 



* ' Astr. Journ.,' No. 179—180. 



