and of the Analysis of the Solar Atmosphere. 251 



latter class of publications by others than by myself, I will now 

 endeavour to complete the historical survey. 



1. Amongst those who have devoted themselves to the ob- 

 servation of the spectra of coloured flames, I must, in the first 

 place, mention Herschel and Talbot. Their names need special 

 notice, as they pointed out with distinctness the service which 

 this mode of observation is capable of rendering to the chemist. 

 For a knowledge of their researches I am mainly indebted to 

 Prof. W. Allen Miller, who gave an extract from them in a lecture 

 republished in the number of the ' Chemical News'' for 19th April, 

 1862. It is there stated that in the volume of the Transactions 

 of the Royal Society of Edinburgh for 1822, at p. 455, Herschel 

 shortly describes the spectra of chloride of strontium, chloride 

 of potassium, chloride of copper, nitrate of copper, and boracic 

 acid. The same observer says, in his article on Light in the 

 Encyclopaedia Metropolitana, 1827, p. 438, — " Salts of soda give 

 a copious and purely homogeneous yellow ; of potash, a beau- 

 tiful pale violet/' He then describes the colours given by the 

 salts of lime, strontia, lithia, baryta, copper, and iron, and con- 

 tinues — " Of all salts the muriates succeed best, from their 

 volatility. The same colours are exhibited also when any of the 

 salts in question are put (in powder) into the wick of a spirit- 

 lamp The colours thus communicated by the dif- 

 ferent bases to flame afford in many cases a ready and neat way 



of detecting extremely minute quantities of them The 



pure earths, when violently heated, as has recently been practised 

 by Lieut. Drummond, by directing on small spheres of them 

 the flames of several spirit-lamps, urged by oxygen gas, yield 

 from their surfaces lights of extraordinary splendour, which, 

 when examined by prismatic analysis, are found to possess the 

 peculiar definite rays in excess which characterize the tints of 

 flames coloured by them ; so that there can be no doubt that 

 these tints arise from the molecules of the colouring matter, 

 reduced to vapour and held in a state of violent ignition." 



Talbot says*, " The flame of sulphur and nitre contains a red 



ray which appears to me of a remarkable nature 



This red ray appears to possess a definite refrangibility, and 

 to be characteristic of the salts of potash, as the yellow ray is of 

 the salts of soda, although, from its feeble illuminating power, 

 it is only to be detected with a prism. If this should be ad- 

 mitted, I would further suggest that whenever the prism shows 

 a homogeneous ray of any colour to exist in a flame, this ray 

 indicates the formation or the presence of a definite chemical 

 compound." Somewhat further on, in speaking of the spectrum 



* Brewster's Journal of Science, v., 1826. Chemical News, April 27, 

 1861. 



