﻿416 M. A. Wullner on the Spectra of 



(1) Beautiful bright double line 62° 42 



(2) Position of the first of three faint lines, ofH ^ a 

 which the second is nearer the first than the third J 



(3) Bright band 63 51 



(4) Bright lioe 64 17 



(5) Bright band 64 22 



(6) Faintly bright line 65 5 



(7) Middle, brightest, of an entire group of lines. 65 47 



(8) Bright line 66 41 



^ (9) Faintly bright line 66 47 



The two aluminium-spectra stand in the same relation to 

 one another as the spectra of the first and second order which 

 MM. Thicker and Hittorf have represented for nitrogen, sulphur, 

 &c. ; the formation of the second at a greater striking-distance 

 and with the use of a Holtz's machine with a condenser proves 

 that it belongs to the higher temperature. 



A comparison of this second aluminium-spectrum with the 

 hydrogen-spectrum described in § 5 shows that they are quite 

 different. Hence it must be assumed that the spectrum con- 

 sisting essentially of the measured six groups of lines is peculiar 

 to hydrogen. 



7. The spectra of hydrogen described in the preceding are es- 

 sentially different. One is not formed from the other by the de- 

 velopment of new lines or new colours as the temperature rises ; 

 but quantities of light disappear which are present at a lower 

 temperature, or on a previously continuously illuminated space 

 bright lines stand out at a higher temperature on an almost 

 black ground ; for, from the mode of formation of the spectra^ it 

 cannot be doubted that the continuous spectrum belongs to 

 the lowest temperature, since the spectrum consisting of three 

 lines, as well as that consisting of six groups of lines, takes the 

 place of the continuous one when the discharges of a Leyden jar 

 are passed through the gas, from which undoubtedly a much 

 greater heating results than from the simple discharge of an in- 

 duction-current. These spectra may, it is true, be formed by the 

 simple current of induction, but only under circumstances which 

 favour such an increase of temperature. The first spectrum is 

 formed if the gas has such a density that the current is best and 

 most completely developed — the six-group spectrum if only mi- 

 nimal quantities of gas are present for the conduction, which can 

 then be raised to the highest temperature, like the particles de- 

 tached from the carbon-points in the electric light. 



This difference of temperature must, in the case of hydrogen, 

 be regarded as the sole cause of this phenomenon ; for a decompo- 

 sition into further elements is not to be thought of. It follows, 



