﻿420 M. A. Wullner on the Spectra of 



the method proposed by Pliicker for producing spectra of the 

 second order — that is, by connecting a Ley den jar with the in- 

 duction-apparatus ; the continuous spectrum then passes at once 

 into that consisting of groups of lines. 



11. The best means, however, of investigating the two new spec- 

 tra is Holtz's machine: by its means the continuous spectrum is 

 obtained without the bright lines of the oxygen-spectrum de- 

 scribed by Pliicker; and it can thus be demonstrated that the 

 spectrum consisting of lines is essentially different from the con- 

 tinuous one — that is. that the latter spectrum emits light which 

 is different from that emitted by the former. 



If the current of a Holtz's machine without its condenser be 

 passed through the tube filled with extremely rarefied oxygen, 

 the light has a sea-green colour, and in the spectrometer only the 

 continuous spectrum is seen without bright lines. Besides a 

 faint reddish field, four beautiful bright fields are first seen, 

 which are sharply bounded and are brightest on the less refran- 

 gible side, and gradually shade off towards the more refrangible 

 side, so that the limits cannot there be sharply defined. For the 

 position of the less refrangible limit, numerous measurements, 

 which only differed by fractions of a minute, gave the following 

 values : — 



O / ii 



(1) Boundary of a yellowish-green field . . 62 50 30 



(2) Boundary of a green field 63 49 00 



This field has the greatest brightness. 



(3) Boundary of a greenish-blue field . . . 64 56 00 



The brightness of this field decreases pretty rapidly in the first 

 quarter; the following three quarters are almost of the same 

 brightness. The breadth of the entire field is about 40'. 



(4) Boundary of a blue-violet field which on thel^p iq 40 

 more refrangible side shades off most beautifully J 



Besides these four fields, a few other less bright ones are seen, 

 which could only be partially measured, and partly were estimated 

 in their position relatively to the brightest fields. 



Between the red field at a and the first green one two nar- 

 row yellowish-green bands were seen, at 62° 25' and 62° 35'. 



Between the fields called above (1) and (2) there is from about 

 63° 20' a feebly bright field, which also is brightest on the less 

 refrangible side, and gradually shades off towards the more re- 

 frangible side. 



At 64° 15' there is a feebly bright field about 10' broad, shaded 

 off in bands. 



From 65° 52' to the bright field (4) the field of view is feebly 



