84 



Mr. C. de Watteville. [May 28, 



On Flame Spectra." By CHARLES DE WATTEVILLE. Communi- 

 cated by ARTHUR SCHUSTER, F.K.S. Keceived May 28, 

 Read June 16, 1904 



(Abstract.) 



In order to obtain the spectrum of any substance, it has generally 

 been considered sufficient to introduce a small quantity of it into an 

 already formed flame. In the course of a photometrical investigation 

 of flames which had been coloured by injecting the spray from saline 

 solutions into the gas to be burnt, M. Gouy discovered in the spectra 

 of the flames several new lines belonging to the metal contained in the 

 solution.* Instead of appearing throughout the whole flame, as did 

 the previously known lines, these new lines were only emitted in the 

 vicinity of the inner blue cone the origin of the Swan spectrum. The 

 observations of M. Gouy were limited to the examination of certain 

 lines of the visible portion of the spectrum, and, with the advice of 

 Professor Schuster, and under his direction, I have taken up this study 

 with the object of extending it, by means of photography, to the ultra- 

 violet portion of the flame, and also of detecting lines which are too 

 feeble to be visible to the eye. 



The method employed for the production of the flame is, in short, 

 that which has been introduced by M. Gouy, and described by him in 

 his memoir, to which reference should be made for a description. The 

 very slight modifications which have been made in the apparatus of 

 this scientist are due to the necessity of having an arrangement which 

 should be as automatic as possible during the 8 hours which were often 

 found necessary for the photographic exposures. These modifications, 

 however, have an important bearing upon the success of the 

 experiments. 



The spectroscopical apparatus used has been of two kinds a fine 

 Rowland concave grating of 1 -metre radius and prism spectroscopes. 

 The results obtained by means of the grating have been completed, as 

 regards the very weak lines, with the help of the prism spectroscope. 



The lines in the spectra obtained under the conditions of my 

 experiments are very much more numerous than is the case when all 

 the portions of the flame do not participate in the production of the 

 phenomena. Sot only are all the lines present which were seen by 



ofessor Hartley in the oxy-hydrogen blowpipe flame, but, in addition, 

 there are a large number of other lines which only extend to the 

 height of the blue inner cone. Moreover, the flame spectra extend 

 sufficiently far into the ultra-violet in order to enable the line 2194 of 

 tin to be observed. 



If we compare the flame spectra thus produced with those of the arc 

 spark, it will be noticed that, as a rule, the lines which are 

 ' Annales de Cliimie et de Phjrque,' 5th Series, vol. 18, 1879. 



