418 



Professor H. H. Turner 



[Jan. y>l, 



W. S. Adams's Results up to November 8, 1918. 



not answer — it led him to impossible results. Clearly something 

 else besides g:ravitv must be at work, and he was driven to the 

 further hypothesis that the radiation-pressure inside the star played 

 an important part in its history. Radiation-pressure (or if we like 

 to call it so, li<ji:ht-pressure) is what makes the tail of a comet. As a 

 comet approaches the sun it begins to feel the effects of the fierce 

 light, which is known to be able to drive away very small particles 

 from the head of the comet, much as we can blow away chaff from 

 wheat. In consequence of this action the small dust-like particles 

 which mav exist in the head are believed to be driven outwards to 



