Spectroscoped and Spectrometed in 1879. Ill 



rently placed lines, may well admit of hope, and persuade to 

 the trial those who have the requisite apparatus. So that they 

 may thus yet be able to do for carbon, what the late lamented 

 Professor Pliicker asserts he did for nitrogen, when by dint 

 of 6-inch sparks and Leyden-jar condensers he changed the 

 form of nitrogen's spectrum from its earlier, or cooler, con- 

 dition of numerous bands composed of innumerable ranks of 

 microscopic linelets, into its now well-known (and first by 



M. Angstrom discovered) linear character of a few much 

 brighter lines only*. 



Spectromety. 



Premising then once more, that though by means of the 

 surpassing brilliancy of end-on vacuum-tubes and large dis- 

 persion, I may be able to give many observed and sharp lines 

 in the green band of tube-carbon (more perhaps than have 

 ever been previously registered for it within the same narrow 

 limits of spectrum place), they form part of only the possible 

 band-spectrum of carbon, our vacuum-tube -carbon, after all — 

 I now propose to append a table of measures to show exactly 

 where the first and second big lines, as well as the numerous 

 little linelets of the compound carbo-hydrogen's green band 

 so signally come in as an addition, when a carbo-hydrogen, 

 and not a carbo-oxygen or carbo-nitrogen, tube is employed. 



Now the first W.N. column in our duplex Table shows the 

 tube-carbon spectrum's green band, as it was seen in a car- 

 bonic-oxide (carbo-oxygen) vacuum-tube. And if we simply 

 add to that spectrum what is given in the second W.N. column, 

 or the blowpipe-flame spectrum's green band, we shall have 

 the tube-carbon green band very nearly as it presents itself in 

 a carbo-hydrogen vacuum-tube. Very nearly, I say only, not 

 quite ; for the actual spectrum observed in the said tube gives the 

 ribbing of the linelets of carbo-hydrogen (between say 49,400 

 and 49,800 W.N. place) clearer and on a darker background 

 than what would result by artificially combining or superim- 

 posing on each other the separately observed carbonic-oxide 

 tube-carbon spectrum and the blowpipe-flame's carbo-hydro- 

 gen spectrum. 



Then in that case carbonic- oxide has added certain weak 

 hazy bands to the fainter and more violet-ward parts of the 



* While copying out this paper for the press I have heard from Prof. 

 Alex. S. Herschel of a inemoir by M. Thalen, the admirable spectrosco- 

 pist of Upsala, who seems to have already obtained, in concert then 



with his now deceased friend M. Angstrom, just such a linear spectrum of 

 carbon. But exactly how, I have yet to learn, as the memoir has not yet 

 arrived in Edinburgh . 



