550 Transactions. — Miscellaneous. 



on the outer layers ; the inside would tend to retain the 

 original rotation of the star. 



38. Thus in the sheared stars there are three tendencies 

 struggling with one another — (1) the original rotation, (2) the 

 new rotation, (3) the tidal action. 



39. But the new rotation would be a large component. 

 We have therefore a star which rotates and shows us alter- 

 nately its hot and cool sides. The old rotation and the tidal 

 motion produce other fluctuations of intensity, and also in- 

 equalities of the rate of motion. 



40. Evidently such a body as described would be a 

 variable star, and for a time such stars would be in pairs. 



41. Many variable stars are in pairs. It is so striking a 

 phenomenon that the probability is one hundred sextillions to 

 one against its being the result of chance. 



42. Conduction, convection, tidal motion, and the con- 

 tending rotations will tend to bring about equality of tempera- 

 ture. This condition of variability will consequently be a 

 temporary one. The star will ultimately become of uniform 

 luminosity. These are all of them known peculiarities of 

 variable stars. 



43. Convection is due to difference of density. This differ- 

 ence may result from differences of temperature, or of chemical 

 composition, or of both. The lake of fire in the sheared star 

 will consist of heavier molecules than the remaining surface, 

 and it will also be at a higher temperature. These two will 

 tend to neutralize each other ; so that equality of temperature 

 due to convection will not be brought about quickly. 



44. Therefore, although such variable stars will doubtlessly 

 become uniform, it is surprising what a number of agencies 

 there are tending to retain this inequality of temperature. 

 On theoretical grounds it appears that this condition of un- 

 equal heating may, as an extreme case, last thousands of 

 years. 



Double Stars. 



45. The work of cutting the stars will be infinitesimal in 

 relation to their available energy before collision. It will not 

 cause any appreciable lessening of the velocity of the escaping 

 stars. But the middle body will exert a powerful attraction. 

 It will exercise a retarding influence, preventing the retreat of 

 the two bodies, equal to that of three times the mass either 

 body loses. Hence, when two bodies lose a third each by im- 

 pact, they do not as a rule become free from the new central 

 body. 



46. If, however, the original proper motion were large, and 

 the graze small, the two stars would escape each other. If 

 the original motion were small, and the graze on an average 



