1 64 STRUCTURE OF THE SUN. PART i. 



to be gaseous, must emit their feeble light from their 

 surfaces alone. All the true clusters of stars which are 

 resolved by the telescope into distinct bright points of 

 light, give a spectrum which does not consist of separate 

 bright lines, but is apparently continuous in its light. 

 The great nebula in Andromeda, which is visible to the 

 naked eye, has an apparently continuous spectrum, but 

 the whole of the red and orange part is wanting, and 

 the brighter parts have a mottled appearance. The 

 easily resolvable cluster in Hercules has a similar 

 spectrum ; Lord Rosse discovered dark streaks or lines 

 in both. 



There is a striking correspondence between the results 

 / of prismatic and telescopic observations ; half of the 

 nebulae which have a continuous spectrum have been 

 resolved into stars, while none of the gaseous nebulse 

 have been resolved even by Lord Rosse's telescope. 

 Thus it appears probable that primordial nebulous 

 matter does exist, according to the theories of Sir 

 William Herschel and La Place. 



The structure of the sun himself, which forms one 

 amidst the multitude of stars which constitute the 

 Milky Way ; and the maintenance of his light and heat 

 without apparent waste, are still in various respects 

 involved in mystery. 



The luminous gaseous atmosphere of the sun is of 

 great extent and of lower temperature, at least in its 

 upper regions, than the photosphere on which it rests. 

 Mr. De la Rue's photographs of the sun show that the 

 light from the border of the solar disc is less intense 

 than that from the equator, on account of the greater 

 depth of solar atmosphere it has to pass through before 

 it reaches the earth, by which a larger portion of the 

 light is absorbed. 



The photosphere of the sun has a mottled appearance, 

 exhibiting minute masses, which must be of enormous 



