﻿210 Prot. A. Lielegg on the Spectra of the 



as near as possible to the slit in the apparatus, exhibited the 

 spectrum of coal-gas with extraordinary sharpness and brilliancy 

 of colour, and furnished the means of observing the live red 

 lines spoken of with great distinctness. 



The successive development of the spectrum of coal-gas, 

 which can be easily proved by comparing the spectra which are 

 produced by a Bunsen's gas-burner, then by coal-gas with 

 oxygen in small quantity, and lastly by coal-gas with oxygen in 

 sufficient quantity to create combustion, leads to the conclu- 

 sion, which has now been known for some length of time, that 

 increase in the temperature of the flame causes a great change 

 in the form of the spectrum ; that is to say, continued aug- 

 mentation of the supply of oxygen adds more and more lines, 

 whilst at the same time greater intensity of light and brilliancy 

 of colour is shown throughout, and this without any percepti- 

 ble appearance of change of an opposite character. Beginning 

 with the flame of a Bunsen's gas-burner, and passing on to the 

 hottest gas-flame inflamed by oxygen, a series of spectra may 

 be followed which show no essential difference, since the dif- 

 ferent degrees of their development cannot be considered such ; 

 for the lines which are produced by Bunsen's gas-burner 

 preserve their position unchanged, other groups being as it 

 were filled in, so that this successive completion of the spec- 

 trum can be distinctly followed as the temperature is increased. 



It can only be ascribed to this gradual change of the spec- 

 trum of coal-gas proceeding from a change of temperature that 

 the group of five lines mentioned above has never before been 

 observed and described as it is in this paper. The flame must 

 be brought, by a sufficient supply of oxygen, to the maximum 

 of its temperature and intensity of light; this group then ap- 

 pears as sharp and distinct as those in the green and blue parts 

 of the spectrum, which become visible at a considerably lower 

 temperature ; in general character also its correspondence with 

 the latter is complete. 



In order to obtain a means of reference, in regard to the 

 position and also the breadth of the red lines and those of the 

 spaces between them, to those of the other lines of the spec- 

 trum, I made a determination of their relative position by 

 means of an illuminated SteinheiPs scale, which divides the 

 space between K a and K /3 into 255 equal parts. The breadth 

 given to the slit was such that that of the sodium-line just filled 

 up the interval between two divisions; this breadth is also that 

 of nearly all the lines which form groups. The apparatus thus 

 employed* (the same which I used in my earlier works) has 



* From the manufactory of mathematical and scientific instruments, by 

 Starke and Kammerer, at the Imperial Polytechnic Institute of Vienna. 



