2^0 Mr. J. N. Lockyer. On the Classification [Jan. 10, 



represents an average case of such a binary star ; both curves starting 

 at the same point. In this case, it will be seen that the companion 

 has almost run through all its stages, whilst the primary has still 

 several stages to pass through. This may be regarded as a more 

 advanced stage of binary stars of Class 2. 



We have here again a severe test, for if these curves represent 

 anything like the truth, the primaries ought in every case to be 

 greenish white, white or yellow. On referring to the list it will be 

 seen that this condition is satisfied in every case. To make quite 

 sure that 8 Herculis belonged to this class of binaries, a special 

 examination of its spectrum was made at Kensington. This showed 

 it to be almost as far advanced along the temperature curve as Sirius. 



Only a small number of such binaries has been recorded. They 

 are as follow : 



Table V. Binary Stars, Class 5. 



IX. Outstanding Cases. 



Out of all the binary stars of which there is any record in Smyth's 

 * Celestial Cycle,' there are only eight which cannot be included in any 

 of the five classes which have been dealt with. Five of these are 

 totally indeterminate on account of the absence of a statement of the 

 colours ; they are as follow : 



