CONTRIBUTIONS FROM THE JEFFERSON PHYSICAL 

 LABORATORY, HARVARD UNIVERSITY. 



THE SPECTRUM OF A CARBON COMPOUND IN THE 

 REGION OF EXTREMELY SHORT WAVE-LENGTHS. 



By Theodore Lyman. 



Presented December 8, 1909. Received January 3, 1910. 



In the region of extremely short wave-lengths discovered by 

 Schumann the spectra of two gases only are easily obtained ; the one 

 is due to hydrogen, the other to some compound of carbon. 1 The 

 hydrogen spectrum consists of a great number of fine lines extending 

 from A 1675 to A 1030; the wave-lengths of the most prominent of 

 these lines have been determined. 2 The carbon spectrum consists 

 of a considerable number of bands extending from the less refrangible 

 end of the Schumann region to the neighborhood of A 1300. The 

 purpose of the present investigation was to measure the position of 

 these bands. 



The results are chiefly valuable because the bands in question fill 

 the gap between A 1854 and A 1675 and form convenient standards of 

 wave-length in a region which up to this time has lacked points of 

 reference. 



The appearance of the spectrum is shown in Plate VIII, Volume 13, 

 of the Memoirs of this Academy. It is marked "Air." The bands 

 are most intense in the less refrangible region, but they are all of the 

 same general type with heads directed toward the region of shorter 

 wave-length. The strongest bands are evidently double. The system, 

 at least throughout its less refrangible part, forms a continuation of 

 the " Fourth group " as described by Deslandres in his paper, " Spectre 

 de bandes ultra-violet des composes hydrogdnds et oxygdnds du car- 

 bone." 3 The spectrum under investigation is thus related to the 

 series of bright bands in the visible and ultra-violet attributed to car- 

 bon monoxide and often observed in ill-prepared vacuum tubes. 



1 Smithsonian Contributions, 1903, 29, No. 1413. 



2 Lyman, Memoirs of this Academy, 1906, 13, 125. 



3 Comptes Rendus, 1888, 106, 842. 



