PHYSICAL BAHfti OF SOLAR CHKMI8TRY. 255 



arc is not continuous like that of the solid carbon points, 

 but consists of a series of vivid bands, each corresponding 

 in color to that particular portion of the spectrum to which 

 its rays belong. Copper gives its system of bands; zinc 

 gives its system; and brass, which is an alloy of copper and 

 zinc, gives a spectrum made up of the bands belonging to 

 both metals. 



Not only, however, when metals are united like zinc 

 and copper to form an alloy, is it possible to obtain the 

 bands which belong to them. No matter how we may 

 disguise the metal allowing it to unite with oxygen to 

 form an oxide, and this again with an acid to form a salt; 

 if the heat applied be sufficiently intense, the bands be- 

 longing to the metal reveal themselves with perfect defi- 

 nition. Into holes drilled in a cylinder of retort carbon, 

 pure culinary salt is introduced. When the carbon is 

 made the positive electrode of the lamp, the resultant 

 spectrum shows the brilliant yellow lines of the metal 

 sodium. Similar experiments made with the chlorides of 

 strontium, calcium, lithium,* and other metals, give the 

 bands due to the respective metals. When different salts 

 are mixed together, and rammed into holes in the carbon, 

 a spectrum is obtained which contains the bands of 

 them all. 



The position of these bright bands never varies, and 

 each metal has its own system. Hence the competent 

 observer can infer from the bands of the spectrum the 

 metals which produce it. It is a language addressed to 

 the eye instead of the ear; and the certainty would not be 

 augmented if each metal possessed the power of audibly 

 calling out, "I am here!" Nor is this language affected 

 by distance. If we find that the sun or the stars give us 

 the bands of our terrestrial metals, it is a declaration on 

 the part of these orbs that such metals enter into their com- 

 position. Does the sun give us any such intimation? 

 Does the solar spectrum exhibit bright lines which we 



* The vividness of the colors of the lithium spectrum is extraor- 

 dinarv; the spectrum, moreover, contained a blue band of indescrib- 

 able splendor. It was thought by many, during the discourse, that I 

 had mistaken strontium for lithium, as this blue band had never 

 before been seen. I have obtained it many times since; and my 

 friend Dr. Miller, having kindly analyzed the substance made use of, 

 pronounces it pure chloride of lithium. J. T. 



