VI 



THE EVOLUTION OF DOUBLE STARS 



(A. H. FISON) 



IN the astronomical discovery of the last twenty years, 

 an increasingly important position has been assumed by 

 the phenomena of double stars. Double stars are so 

 richly distributed over the heavens as to indicate that 

 the cosmic process by which they have been developed is 

 a common one and that it has taken place in all parts of 

 the physical universe. In the present lecture I propose 

 to describe the general results of some recent researches 

 that appear to suggest what this process has been, and, 

 although it is certain that the actual conditions existing 

 in nature are far from being so simple as those it is 

 necessary to assume as a basis for mathematical reason- 

 ing, we meet with so many features of systems of 

 double stars that are in such admirable harmony with the 

 deductions from theory, that it is impossible not to regard 

 the theory as expressing in its essential features an 

 important cosmical process. 



The discovery of double stars followed as a necessary 

 consequence of the invention of the telescope. It was 

 soon found that there were many stars that, while 

 seeming single to the naked eye, appeared in the field of 

 the telescope as two stars close together. Such an appear- 

 ance may obviously be due to either of two causes. The 

 two stars may be really close together, in which case 



