262 M. G. Kirchhoff on the History of Spectrum Analysis. 



the special absorbing power anticipated. I have the impression 

 that some Frenchmen did make this out by experiment, but I 

 can find no reference on that point. 



" I am not sure whether Prof. Stokes's suggestion of a 

 mechanical theory has ever appeared in print. I have given it in 

 my lectures regularly for many years, always pointing out along 

 with it that solar and stellar chemistry were to be studied by 

 investigating terrestrial substances giving bright lines in the 

 spectra of artificial flames corresponding to the dark lines of 

 the solar and stellar spectra." 



At page 158 of the Philosophical Magazine for February 

 1862, Professor Thomson says, "The last eight or nine years 

 Stokes's principles of solar and stellar chemistry have been 

 taught in the public lectures on natural philosophy in the 

 University of Glasgow ; and it has been shown as a first result, 

 that there is certainly sodium in the sun's atmosphere. The 

 recent application of these principles in the splendid researches 

 of Bunsen and Kirchhoff (who made an independent discovery 

 of Stokes's theory) has demonstrated with equal certainty that 

 there are iron and manganese, and several of our other known 

 metals, in the sun." 



From the above letter, which at my desire was printed in the 

 Philosophical Magazine, S. 3. vol. xx. p. 20, and translated into 

 the Annates de Chimie et de Physique ,*ser. 3. vol. lxii. p. 190, it is 

 clear that many years ago Stokes in conversation had thrown 

 out the idea that it would perhaps be possible to argue from the 

 dark lines of the solar spectrum concerning the chemical consti- 

 tution of the atmosphere of the sun. That this idea is correct — 

 that a flame does, in fact, exert the absorption which Stokes 

 ascribed to it, and that from the bright lines in the spectrum of 

 an incandescent gas the chemical components of the gas can 

 with certainty be deduced — was first proved by my theoretical 

 considerations, and by experiments which I have made partly in 

 conjunction with Bunsen, and partly alone. Hence it appears 

 that no one had formerly (during a period of ten years) published 

 anything concerning the opinion which Stokes expressed in 

 conversation. In singular contradiction to this, stands Prof. 

 Thomson's recent statement, "that Stokes's principles of solar 

 chemistry have shown as a first result, that there certainly is 

 sodium in the sun's atmosphere;" and further, "The recent ap- 

 plication of these principles by Bunsen and Kirchhoff (who made 

 an independent discovery of Stokes's theory) has demonstrated 

 with equal certainty the presence of other metals in the sun "*. 



Heidelberg, November 1862. 



[* In a lecture delivered at the Royal Institution on April 12, 1862, I 

 stated, with reference to this question (see ■ Chemical News/ May 24, 



