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racteristic of the salts of potash, as the yellow ray is of the salts of 
soda. If this should be admitted , I would further suggest that when- 
ever 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 .” 
Further on, speaking of the spectrum of red fire (such as is used 
in theatres and in fireworks), I said, “the other lines may be attri- 
buted to the antimony, strontia, &c., which enter into this compo- 
sition. For instance, the orange ray may be the effect of the 
strontia, since Herschel found in the flame of muriate of strontia a 
ray of that colour If this opinion should be correct, and appli- 
cable to the other definite rays, a. glance at the prismatic spectrum 
of a flame may show it to contain substances which it would otherwise 
require a laborious chemical analysis to detect .” 
An early paper by Herschel has been omitted in its proper place, 
the year 1822 (Transactions Eoyal Society of Edinburgh, vol. ix. 
p. 455). He there shortly describes the spectra of chloride of 
strontia, chloride of potassa, chloride of copper, nitrate of copper, 
and boracic acid. 
In 1827 (after the publication of my experiments in 1826), he 
stated in the Encyclopedia Metropolitana, article on Light, p. 438, 
that salts of soda give a copious and purely homogeneous yellow ; 
those of potash a beautiful pale violet. He also describes the 
spectra of lime, strontia, lithia, barytes, copper, and iron. 
In another paper of mine (Phil. Mag. 1834, vol. iv. p. 114), the 
flames of strontia and lithia are examined. The following is an 
extract from this paper: — “The strontia flame exhibits a great 
number of red rays, well separated from each other by dark inter- 
vals, not to mention an orange, and a very definite bright blue ray. 
The lithia exhibits one single red ray. Hence I hesitate not to 
say that optical analysis can distinguish the minutest portions of 
these two substances with as much certainty, if not more, than 
any other known method.” 
Another passage, taken from the same page, records the first 
observation of those peculiar rays at the violet end of the spectrum, 
to which some years later Herschel gave the name of the lavender 
rays. “ The flame of Cyanogen separates the violet end of the 
spectrum into three portions, with broad dark intervals between. 
