242 POPULAR SCIENCE MONTHLY. 



from our ordinar}' conception of a gas. That which we see, which gives 

 tlie snn its apparent size, which sends us our light, is known as the 

 photosphere. This is probably a brilliant shell of metallic clouds float- 

 ing in an atmosphere of vapors of the same materials. There are cer- 

 tain details in this photosphere with which we are familiar, such as 

 l)right patches, known b}^ different names, and sun-spots. For con- 

 venience we may regard this photosphere and all that it contains as 

 the Sun, and all that lies outside this shell as the solar atmosphere. 

 With the sun itself we have little to do in this article, since it can be 

 better observed on any clear day than at time of eclipse. It is, how- 

 ever, only at time of total eclipse that we clearly see all those strange 

 and complex features which make up what we have called the solar 

 atmosphere. In our study of it, however, we must not be governed 

 too much by any analogy with our own atmosphere. Lying next to 

 the body of the sun is a layer of crimson flame, known as the chromo- 

 sphere, which has a thickness of perhaps 5,000 or 6,000 miles. This 

 may seem like a great depth for such a sea of fire, but compared with 

 the enormous size of the sun it is very small indeed, and forms but 

 a thin rose-colored rim about the edge of the sun. At the bottom of 

 this is probably the so-called reversing layer. The solar spectrum is 

 crossed by dark lines due to the elements which there exist. By these 

 dark absorption lines, which are seen in the ordinary solar spectrum, 

 the presence is known of many familiar elements. The higher regions 

 of the chromosphere are less complex and consist in large part of 

 hydrogen. From these regions, by forces which there operate, great 

 masses of brilliant colored gas are throwTi upward to enormous dis- 

 tances, in general 10,000, or 20,000 miles, but often much higher, even 

 to 200,000 or 300,000 miles. Eesting also on the photosphere is the 

 corona, which extends its pearly light outward from the sun to immense 

 distances which must be reckoned in millions of miles. 



The different parts of the solar atmosphere are brightly luminous, 

 and stand forth in splendid beauty at the instant of totality. The 

 only reason why we do not see them on any clear day is that they are 

 lost in the blinding light of the central sun. The sun's face must be 

 shut out. This service is rendered by the moon at an eclipse. At 

 other times the chief trouble is not that the sun shines directly into 

 our eyes, since a piece of cardboard could be so placed as to cut off the 

 rays. The real difficulty arises from the presence of our atmosphere, 

 which becomes so bright from the diffused light of the sun, that the 

 solar appendages are lost to view. This will be apparent from the 

 daily phenomenon of the appearance by night, and the disappearance 

 by day, of the stars. They are shining just as brightly by day as by. 

 night, and could be seen perfectly well if the atmosphere were removed 

 for a moment. 



