166 [June 19, 



which could be closed by a plate of quartz ; the ends of the tube 

 were closed by ground brass plates, each supporting a pair of brass 

 forceps, into which the electrodes were fitted ; through the axis of the 

 tube a current of each gas was transmitted at the ordinary atmo- 

 spheric pressure. 



Among the gases thus tried were hydrogen, protoxide of nitrogen, 

 carbonic acid, carbonic oxide, olefiant gas, marsh-gas, cyanogen, 

 sulphuretted hydrogen, sulphurous acid, nitrogen, and oxygen. The 

 spectrum obtained from the same metal varied considerably in these 

 different media. In hydrogen the intensity of the spectrum was 

 greatly reduced, and the more refrangible rays were wanting, but 

 no new rays made their appearance. In carbonic acid, carbonic 

 oxide, olefiant gas, marsh-gas, and cyanogen, the special lines due to 

 the metal were produced, but in each a series of identical lines 

 appeared, and these new lines were referable to the carbon con- 

 tained in each of these gases. Each gas exhibits special lines which 

 are continued across the spectrum, and are never interrupted like 

 those of the metals. 



The author observed that many of these gases, such as protoxide 

 of nitrogen, hydrochloric and sulphurous acid, presented a consider- 

 able obstacle to the passage of the sparks from the induction-coil. 



X. " On the Long Spectrum of Electric Light/' By Professor 

 GEORGE G. STOKES, M.A., Sec. U.S. &c. Received June 



19, 1862. 



(Abstract.) 



The author's researches on fluorescence had led him to perceive 

 that glass was opaque for the more refrangible invisible rays of the 

 solar spectrum, and that electric light contained rays of still higher 

 refrangibility, which were quite intercepted by glass, but that quartz 

 transmitted these rays freely. Accordingly he was led to procure 

 prisms and a lens of quartz, which, when applied to the examination 

 of the voltaic arc, or of the discharge of a Leyden jar, by forming a 

 pure spectrum and receiving it on a highly fluorescent substance, 

 revealed the existence of rays forming a spectrum no less than six 

 or eight times as long as the visible spectrum. This long spectrum, 

 as formed by the voltaic arc with copper electrodes, was exhibited 



