1906.] on Eclipse Problems mid Observations. 233 



tion does actually exist. Poynting has shown us how to deal with it, 

 and has given us numbers showing how small bodies in the sol:;r 

 system would be affected by the radiation of the sun. 



Adopting the figures which Poynting has given us, I have pr - 

 pared a table showing the temperature attained by small particles put 

 in the neighbourhood of the sun. There has been an enormous 

 advance in the domain of radiation in the last fifteen years. A 

 number of workers have contributed. Those foremost on th.* 

 experimental side have been Paschen, and Lummer, and Kurlbaum. 



Putting together various numbers determined by them, and by other 

 workers before them, we come to the conclusion that the best 

 number which we can adopt for the temperature of the sun's surface 

 is 6200° C, measured from the absolute zero. Then, for certain 

 distances from the sun's surface measured by millions of miles, the 

 table shows the temperature which would be attained by bodies held 

 at different distances from the sun's surface. At between three and 

 four millions of miles the temperature has fallen to the temperature 

 of molten iron. 



Now, observe that the rise of temperature is not very quick at 

 first as we pass from the earth to the sun, but it becomes very quick 

 in the last three million miles, as we pass in towards the surface of 

 the sun. Bodies attracted by the sun from a distance move more 

 and more quickly the nearer they approach the sun. Therefore, we 

 may take it that where the bodies are moving most rapidly, near the 

 sun, there is the greatest change of temperature. If things are 

 moving quickly through rapidly changing temperatures, we shall be 

 sure to have the splintering and vaporising of those bodies by the 

 action of the rapid rise of temperature. 



Let us apply to the splinters and vapours the ideas that we have 

 got from the pressure of radiation. Arrhenius, the Swedish savant, 

 has not hesitated to suggest that the repulsion of comets' tails is an 

 instance of repulsion by light. A comet going round the sun shows 



