268 ELEMENTS OF GEXEEAL SCIENCE 



The spectroscope is an instrument which makes it possible 

 to analyze the light received from any source. When the 

 light of the sun has been analyzed, it is found that in its 

 atmosphere there are certainly about half of the elements 

 of which the earth is composed. Among them are such 

 familiar things as hydrogen, carbon, oxygen, potassium, cal- 

 cium, iron, nickel, copper, zinc, silver, tin, and lead. Most 

 of the elements known on the earth which have not been 

 found in the sun are the nonmetals, such as chlorine, iodine, 

 sulphur, nitrogen, and phosphorus. Although they have not 

 been found upon the sun, they probably exist there. Perhaps 

 there' are a few heavy metals, such as gold, mercury, and 

 platinum, which have not been discovered in the sun. These 

 heavy substances probably lie so deep in its interior that 

 the light from them does not get beyond its surface. It is 

 possible that as the storms on the sun bring more deeply 

 placed materials to the surface, many elements not yet 

 recognized may later be detected. 



272. Nature and distance of the stars. It was once sup- 

 posed that the sky is composed of a more or less solid sub- 

 stance in which the stars are embedded as jewels and that 

 the whole structure revolves about the earth. We now know 

 that the earth turns on its own axis and that it revolves in 

 its orbit about the sun. We also know that the other bodies 

 have motions more or less similar to those of the earth. 

 The stars are so far away from us that their position rela- 

 tive to one another seems to us to change but little. The posi- 

 tion of the planets relative to the stars changes constantly. 

 By this fact the planets, although they look like stars and 

 are often so called, can readily be distinguished from the 

 stars ; the stars form a relatively permanent pattern, but after 

 a few days or weeks the planets can be seen to have changed 

 position among them. 



The stars are immense suns, most of those we see being 

 much larger than our sun and millions of times larger than 



