208 



From Newton to Kirchoff. 



Melville and Talbot stood at opposite ends of three 

 quarters of a century ; how exceeding slow had been the 

 progress of discovery ! But at this point in its history the 

 science of photochemical analysis was suddenly electrified 

 into life, and thenceforth the rapidity of its progress has 

 amazed the world. 



The beauty of Mr. Talbot's crimson flame was quickly 

 eclipsed by the more brilliant effects of the electric arch. 

 In 1855, Sir Charles Wheatstone announced the capital 

 discovery that the light from white hot metallic poles of a 

 powerful electric battery when passed through a prism gives 

 a spectrum strangely different from that of solar light. 

 Whereas the brilliant colors of the latter are interrupted by 

 delicate lines of almost total darkness, the more subdued 

 lines of the former are crossed at intervals by colored lines 

 of almost dazzling beauty and brightness. Moreover, it 

 was seen that the number, color and position of these 

 brilliant bars were peculiar to each metal employed, so that, 

 as Sir Charles remarked, " We have here a method of 

 detecting the presence of metallic bodies more .easily applica- 

 ble even than a chemical examination." This idea, de- 

 veloped by the labors of many patient and devoted chemists, 

 seconded by the skill of the ablest opticians, has resulted in 

 the elegant modern system of analysis by the spectroscope, 

 an instrument the delicacy and accuracy of whose announce- 

 ments are unsurpassed. 



We have no room in this brief article to even name the 

 many scientists whose labors have contributed to this happy 

 result, much less can we indulge in any discussion of the 

 principles of the new and elegant science of spectrum 

 analysis. The briefest statement of a few of its most funda- 

 mental facts must suffice. Such are the following: 



A. The light from the incandescent vapors of an element, 

 when passed through a prism, gives a spectrum consisting 

 of bright lines : 



