17 



Look at the figure of the sun in the frontispiece. The 

 picture represents an eclipse of the sun; the dark body of the 

 moon has screened the sun's shining disc and taken the glare out 

 of our eyes; we see a silvery halo surrounding the great orb on 

 every side. It is the sun's atmosphere, or "crown" (corona), 

 stretching for millions of miles into space in the form of a soft 

 silvery-looking light; probably much of its light is sunlight 

 reflected from particles of dust, although the spectroscope shows 

 an element in the corona that has not so far been detected any- 

 where else in the universe and which in consequence has been 

 named Coronium. 



We next notice in the illustration that at the base of the halo 

 there are red flames peeping out from the edges of the hidden 

 disc. When one remembers that the sun is 866,000 miles in 

 diameter, one hardly needs to be told that these flames are really 

 gigantic. We shall see what they are presently. 



Regions of the Sun 



The astronomer has divided the sun into definite concentric 

 regions or layers. These layers envelop the nucleus or central 

 body of the sun somewhat as the atmosphere envelops our earth. 

 It is through these vapour layers that the bright white body of 

 the sun is seen. Of the innermost region, the heart or nucleus of 

 the sun, we know almost nothing. The central body or nucleus 

 is surrounded by a brilliantly luminous envelope or layer of 

 vaporous matter which is what we see when we look at the sun 

 and which the astronomer calls the photosphere. 



Above that is, overlying the photosphere there is a second 

 layer of glowing gases, which is known as the reversing layer. 

 This layer is cooler than the underlying photosphere; it forms a 

 veil of smoke-like haze and is of from 500 to 1,000 miles in 

 thickness. 



A third layer or envelope immediately lying over the last one 

 is the region known as the chromosphere. The chromosphere 



