110 Mr. Piazzi Smyth on Carbon and Carbo- Hydrogen, 



six tubes, viz. air, nitrogen, oxygen, ozone, hydrogen, and ni- 

 trous oxide, we shall find little or nothing unusual therein, 

 but only see the fainter and still more faint prolongations of 

 the green band going off in that violet-ward direction. 



In cyanogen, carbonic acid, and carbonic-oxide tubes, how- 

 ever, there is something suspicious that in one certain spot in 

 each of them — as far beyond, or violet-ward, of the crossing- 

 place of lines as that is from the strong red-ward beginning 

 of the tube-carbon's green band, there is a sort of smear, or 

 half rubbed-out line — in fact, looking more like an impurity 

 trace than a proper constituent of the chemical compound 

 under trial. 



But in the alcohol and olefiant gas-tubes (and even in the 

 marsh-gas as well, though not so strongly) that sort of chalked 

 place is occupied by a brilliant colossal bright line, so glaring 

 that it almost extinguishes by its superior light the fine thin 

 lines of the tube-carbon band in the neighbourhood. And 

 twice as far onward, still in the direction of increased refran- 

 gibility (or violet-ward), there is another similar and, though 

 less bright line, still a very notable one to meet with in that 

 part of the spectrum. 



Now what are these two bright lines which appear so con- 

 spicuously in all three of our carbo-hydrogen tubes, but in no 

 other compounds of carbon, though we have been hitherto 

 told by several famous observers that there is no difference 

 amongst any of them ? 



By most careful reference from the electrically illuminated 

 vacuum-tubes to the blowpipe flame, I ascertained that the 

 strangers were the first and second lines of the green band of 

 the coal-gas and air blowpipe-flame. Proving that even at 

 induction-spark temperature that remarkable and humanly 

 most useful compound, carbo-hydrogen, excitable at first by 

 merely the flame of the smallest candle, is not yet completely 

 dissociated into its elements. 



Perhaps more powerful sparks than the one-inch ones em- 

 ployed by me might dissociate the whole of the carbo-hydro- 

 gen in the tube ; and then we should have only the tube-carbon 

 bands and hydrogen- lines with some possibility of impurities, 

 while the poor old blowpipe-flame's spectrum would be no- 

 where. And whether some immensely and still more pow- 

 erful and also jar-condensed electric sparks may not be able 

 yet further even to break down the already described tube- 

 carbon spectrum with its bands (composed really of innume- 

 rable and closely-packed, but very thin, sharp lines and line- 

 lets), and produce a second and linear spectrum of carbon 

 composed probably of a few only, and far brighter and diffe- 



