ADDBESS. 25> 



Professor G. Darwin, in his investigation of the equiHbrium of a rotat- 

 ing mass of fluid, found, in accordance with the independent researches 

 of Poincare, that when a portion of the central body becomes detached 

 through increasing angular velocity, the portion should bear a far larger 

 ratio to the remainder than is observed in the planets and satellites of the 

 solar system, even taking into account heterogeneity from the condensa- 

 tion of the parent mass. 



Now this state of things, in which the masses though not equal are of 

 the same order, does seem to prevail in many nebute, and to have given 

 birth to a large class of binary stars. Mr. See has recently investigated 

 the evolution of bodies of this class, and points out their radical difiierences 

 from the solar system in the relatively large mass-ratios of the component 

 bodies, as well as in the high eccentricities of their orbits brought about 

 by tidal friction, which would play a more important part in the evolution 

 of such systems. 



Considering the large number of these bodies, he suggests that the solar 

 system should perhaps no longer be regarded as representing celestial 

 evolution in its normal form — 



' A goodly Paterne to whose perfect mould 

 He fashioned them . . .' 



but rather as modified by conditions which are exceptional. 



It may well be that in the very early stages condensing masses are 

 subject to very different conditions, and that condensation may not always 

 begin at one or two centres, but sometimes set in at a large number of 

 points, and proceed in the different cases along very different lines of 

 evolution. 



Besides its more direct use in the chemical analysis of the heavenly 

 bodies, the spectroscope has given to us a great and unexpected power of 

 advance along the lines of the older astronomy. In the future a higher 

 value may, indeed, be placed upon this indirect use of the spectroscope 

 than upon its chemical revelations. 



By no direct astronomical methods could motions of approach or of 

 recession of the stars be even detected, much less could they be measured. 

 A body coming directly towards us or going directly from us appears to 

 stand still. In the case of the stars we can receive no assistance from 

 change of size or of brightness. The stars show no true discs in our 

 instruments, and the nearest of them is so far off that if it were approach- 

 ing us at the rate of a hundred miles in a second of time, a whole 

 century of such rapid approach would not do more than increase its 

 brightness by the one-fortieth part. 



Still it was only too clear that, so long as we were unable to ascertain 

 directly those components of the stars' motions which lie in the line of 

 sight, the speed and direction of the solar motion in space, and many of 



