100 J. N. Lockyer on the supposed Compound 
Application of these Considerations to Known Compounds, 
Now to apply this reasoning to the dissociation of a known 
compound body into its elements.— 
A compound body, such as a salt of calcium, has as definite 
a spectrum as a simple one; but while the spectrum of the 
metal itself consists of lines, the number and thickness of some 
of which increase with increased quantity, the spectrum of the 
compound consists in the main of channelled spaces and bands, 
which increase in like manner. 
In short, the molecules of a simple body and a compound 
one are affected in the same manner by quantity in so faras 
their spectra are concerned ; zn other words, both spectra have ther 
ng and short lines, the lines in the spectrum of the element 
being represented by bands or fluted lines in the spectrum of 
the compound ; and in each case the greatest simplicity of the 
spectrum depends upon the smallest quantity, and the greatest 
complexity (a continuous spectrum) upon the greatest. 
The heat required to act upon such a compound as a salt of 
calcium so as to render its spectrum visible, dissociates the 
compound according to its volatility; the number of true me- 
tallic lines which thus appear is a measure of the quantity of 
the metal resulting from the dissociation, and as the metal lines 
increase in number, the compound bands thin out. . 
ave shown in previous papers how we have been led to — 
the conclusion that binary compounds have spectra of their 
own, and how this idea has been established by considerations 
having for a basis the observations of the long and short lines 
It is absolutely similar observations and similar ante a 
which I have to bring forward in discussing the compouné — 
nature of the chemical elements themselves. 
In a paper communicated to the Royal Society in 1874, refer _ 
ring, among other matters, to the reversal of some lines in the _ 
solar spectrum, I remarked,*— : 
“It 1s obvious that greater attention will have to be give? — 
to the precise character as well as to the position of each of the 
Fraunhofer lines, in the thickness of which I have already ob 
served several anomalies. I may refer more particularly a 
trum (I might have added that they were by far the thicket! 
lines in the solar spectrum] than the largest calcium line of 
this region (4226°3), this latter being invariably thicker than 
he H | oto: of th i od 
remaining, moreover, visible in the spectrum of substances 000 
taining calcium in such small quantities as not to show ay — 
traces of the H lines, a 
7 
* Phil. Trans., vol. clxiv, part 2, p. 807. 3 
