DOUBLE STARS 141 



view that is at first naturally suggested sees in them two 

 stars, originally independent, that, happening to approach 

 each other, have been since kept together by their mutual 

 attraction. In such a case, however, the stars would gain 

 as the result of their attraction during their approach suffi- 

 cient velocities to carry them back to their original 

 positions, however remote these were, a law illustrated 

 in the rush of comets through the solar system. Further, 

 the chance of two stars isolated in space being drawn 

 together at all seems far too small to account for the exist- 

 ence of so large a proportion of doubles, while the same 

 process would lead to a rich distribution of triple, quadruple, 

 and more complicated systems, and all these are extremely 

 rare. We are therefore led to inquire whether the com- 

 ponents of a double star may not have been physically 

 related from the first, and to endeavour to imagine some 

 process by which, in accordance with known physical 

 laws, they may have been developed from a parent mass. 

 In 1755, the German philosopher Immanuel Kant, 

 descending for a time from the sublime heights of the 

 Critical Philosophy, imagined a scheme by which the 

 Solar System might have been developed by the opera- 

 tion of natural law upon a vast cosmic cloud. Forty-one 

 years later, a speculation of essentially the same character 

 was suggested by Laplace, and, owing to his higher 

 authority as a mathematician and as an astronomer, it 

 has since been generally associated with his name. Ac- 

 cording to Laplace, the matter now composing the Sun 

 and planets existed at one time as an intensely heated 

 mist, which extended beyond the present limits of the 

 system. This nebula would have been spherical, but 

 for the fact that it possessed a motion of rotation round 

 a diameter, and this, by the action of centrifugal force, 

 caused it to become spheroidal, flattened along the axis of 



