146 SCIENTIFIC RECREATIONS. 



know mat masses ot" metal are ever boiling up from the lower and hotter 

 levels of the sun's atmosphere to the cooler upper regions, where they must 

 again form clouds to throw out their light and heat, and to absorb the light 

 and heat coming from the hotter lower regions ; then they become con- 

 densed, and are drawn back again towards the body of the sun, so forming 

 those remarkable dark spaces or sunspots by their down rush to their former 

 levels. In these vast changes we have abundant cause for those magnetic 

 changes which we observe at the same instant at distant points on the 

 surface of the earth." So we are indebted to the Spectroscope for many 

 wonderful results the constitution of the stars, whether they are solid or 

 gaseous, and many other wonders. 



The manner in which we have arrived at these startling conclusions is 

 not difficult to be understood, but some little explanation will be necessary. 



The existence of dark lines in the solar spectrum proves that certain 

 rays of solar light are absent, or that there is less light. When we look 

 through the prism we perceive the spaces or lines, and we can produce these 

 ourselves by interposing some substance between the slit in the shutter 

 before mentioned and the prism. The vapour of sodium will answer our 

 purpose, and we shall find a dark line in the spectrum, the bright lines being 

 absorbed by the vapour. We can subject a substance to any temperature 

 we please, and into any condition solid, liquid, or gaseous ; we can also 

 send the light the substance may give out through certain media, and we can 

 photograph the spectrum given out under all conditions. The distance of the 

 source of the light makes no differenec. So whether it be the sun, or a far- 

 distant star, we can tell by the light sent to us what the physical condition 

 of the star may be. It was discovered in 1864 tna t the same metallic body 

 may give different spectra ; for instance, the spectrum might be a band of 

 light, like the rainbow, or a few isolated colours ; or again, certain 

 detached lines in groups. The brightness of the spectrum lines will change 

 with the depth of the light-giving source, or matter which produces it. 



We have become aware by means of the Spectroscope that numerous 

 metals known to us on earth are in combustion in the sun, and new ones 

 have thus been discovered. In the immense ocean of gas surrounding the 

 sun there are twenty-two elements as given by Mr. Lockyer, including iron, 

 sodium, nickel, barium, zinc, lead, calcium, cobalt, hydrogen, potassium, 

 cadmium, uranium, strontium, etc. Not only is the visible spectrum capable 

 of minute examination, but, as in the case of the heat spectrum already 

 mentioned when speaking of Calorescence, the light spectrum has been traced 

 and photographed far beyond the dark space after the blue and violet rays, 

 seven times longer than the visible solar spectrum a spectrum of light 

 invisible to our finite vision. Although a telescope has been invented for 

 the examination of these " ultra violet " rays, no human eye can see them. 

 But and here science comes in when a photographic plate is put in 

 place of the eye, the tiniest star can be seen and defined. Even the 

 Spectroscope at length fails, because light at such limits has been held to 



