A STUDY WITH THE ECHELON SPECTROSCOPE OF CER- 

 TAIN LINES IN THE SPECTRA OF THE ZINC ARC 

 AND SPARK AT ATMOSPHERIC PRESSURE. 



By Norton A. Kent. 

 Presented l^y Charles R. Cross. Received June 19, 1912. 



In November, 1907, the writer published, in collaljoration with one 

 of his graduate students, an article ^ attempting to meet certain 

 objections made by Keller ^ to the method of procedure adopted by 

 the writer in certain former work ^ upon the question of the relative 

 wave-lengths of certain lines in the spectrum of titanium and zinc as 

 developed by the arc and spark discharge in air at normal pressure. 

 That displacements of the spark lines to the red from the position of 

 the corresponding arc lines actually existed on the photographic plates 

 obtained, is regarded by the writer as unquestionably proven. It is 

 certain, also, that the displacements were not due to any incorrect 

 experimental procedure. 



It appeared to be worth while to study the matter further, seeking 

 to ascertain, if possible, the cause of these displacements. As the 

 echelon spectroscope had revealed structure in the lines of metal- 

 lic spectra both in Pliicker tubes and in the arc in vacuo and at 

 normal atmospheric pressure*, it seemed advisable to use this in- 

 strument to study the spark, noting the change in the form of the 

 image as a function of the constants of the electric circuit. The 

 titanium lines XX 3900 and 3913, formerly studied in detail, presented 

 difficulties because of their short wave-lengths; therefore, it appeared 

 best to concentrate the work upon zinc. 



A brief survey of the most important results in the case of this metal 

 recently obtained by various observers is thus in order. 



1 These Proceedings, 43, No. 11, Nov. (1907). 



2 Ueber die angeblicke Verschiebung der Fuiikenlinien, Inaugural Disserta- 

 tion, Christian Keller. 



3 These Proceedings, 41, No. 10, .lulv (190.5). 



4 Janicki, Annalen der Physik, 19, 36-79, Jan. (1906). 

 Nutting, Astrophvsical .lournal, 23, No. 1, Jan. (190t)) 

 Nutting, Bulletin Bureau of .Standards. 2, No. 3, Dec. (1906). 



