138 SPECTRUM OF THE ELECTRIC SPARK. PAKT i. 



right time from the appearance of the flame which 

 issued from the mouth of the converting vessel, but now 

 Professor Roscoe has determined the exact moment for 

 cutting off the blast by a spectral examination of the 

 flame, the light of which is most intense. The flame 

 spectrum in its various phases revealed complicated 

 masses of dark absorption bands and bright lines, show- 

 ing that a variety of substances were present in the flame 

 in a state of incandescent gas ; and by a simultaneous 

 comparison of these with well-known spectra of certain 

 elementary bodies, Mr. Eoscoe ascertained the presence 

 of sodium, potassium, lithium, iron, carbon, phosphorus, 

 hydrogen, and nitrogen in the flame. 



Both Dr. Wollaston and Fraunhofer noticed that the 

 spectrum of the electric spark was crossed by bright- 

 coloured lines ; and in the year 1835, Professor Wheat- 

 stone determined the spectra of the electric spark taken 

 from fused zinc, cadmium, tin, bismuth, lead, and from 

 mercury, and found that each is crossed by bright lines 

 differing in number, position, and colour, but which are 

 the same whether the electric spark be from a static, 

 voltaic, or magneto-electric machine. Having given a 

 plate showing the colours of these bright lines on the 

 respective spectra, he proved that they are not owing to 

 the electricity, but to the incandescent atoms of the 

 metals, for by using different metals as terminals to the 

 conducting wires, he determined the spectra of these 

 metals in vacuo, which proved that they were due alone 

 to the volatilization of the metallic terminals, and con- 

 cluded that any one metal may be distinguished from 

 another by the appearance of the spark. 



Wheatstone discontinued his spectrum researches, for 

 he had invented the electric telegraph, and was busy in 

 extending the first telegraphic wire that ever carried 

 the thought of man to man between London and Man- 

 cheater. Soon after he laid the first aquatic line across 



