THE SUN. 63 



values which have been derived from the velocity 

 of light, and from the constant of aberration, 

 are fairly in agreement with those derived from 

 direct measurement. On the whole, the most 

 probable value of the parallax is about 8" "8, 

 indicating a mean distance of about 92,700,000 

 miles, with a " probable error" of about 150,000 

 miles. 



What a different picture the sun presents to 

 us at the beginning of the twentieth century 

 from that which it presented to Herschel and 

 his contemporaries at the beginning of the 

 nineteenth ! To Herschel, the Sun was a cool 

 dark globe, surrounded by a luminous atmosphere. 

 As the outcome of the researches and discoveries 

 outlined in this chapter, the Sun is now seen 

 to be a vast central world, which is over a 

 million times larger than the Earth. In the 

 words of an able writer, "It is most prob- 

 ably a world of gases, where most of the metals 

 and metallic bases that we know exist only as 

 vapours, even at the Sun's surface, hotter 

 than any furnace on earth, and getting a still 

 fiercer heat for every mile of descent lower. 

 Of that heat in the Sun's interior we can 

 form no conception. The pressure within the 

 Sun is equally inconceivable. A cannon - ball 

 weighing 100 Ib. on earth would weigh 2700 



