-and on those produced by the Earth’s Atmosphere, Sc. 391 
spectrum is 15}inches. Mine, upon the same scale, is nearly 
17 inches. The length of the general spectrum, which I have 
delineated, is about five feet 8 inches, and the length of a 
spectrum, corresponding to the scale on which I have deline- 
ated parts of it, is seventeen feet. 
Fraunhofer has laid down in his map 354 lines, but in the 
delineations which I have executed, the spectrum is divided 
into more than 2000 visible and easily recognised portions, 
separated from each other by lines more or less marked, ac- 
cording as we use the simple solar spectrum, or the solar and 
gaseous spectrum combined, or the gaseous spectrum itself, in 
which any breadth can be given to the dark spaces. 
The suggestion of Mr. Talbot induced me to watch nar- 
rowly the state of the defective solar lines at different seasons 
of the year, in order to observe if any change took place in 
the combustion by which the sun’s light is generated, or in the 
solar atmosphere through which it must pass. Such changes 
I have found to be very general in every species of terrestrial 
flame. The definite yellow rays which exist in almost all 
white lights, flicker with a variable lustre; and analogous rays 
in the green and blue spaces proceeding from the bottom of 
the flame, exhibit the same inconstancy of illumination. In 
the course of the winter observations, I observed distinct lines 
and bands in the red and green spaces, which at other times 
wholly disappeared; but a diligent comparison of these ob- 
servations soon showed, that these lines and bands depended 
on the proximity of the sun to the horizon, and were produced 
by the absorptive action of the earth’s atmosphere. I have no 
hesitation, therefore, in affirming, that during the period of 
my own observations, no change has taken place either in 
the dark lines or luminous bands of the solar spectrum; a 
result which seems to indicate, that the apparent body of 
the sun is not a flame in the ordinary sense of the word, 
but a solid body raised by intense heat to a state of bril- 
liant incandescence. ) 
The atmospheric lines, as they may be called, or those lines 
and bands which are absorbed. by the elements of our atmo- 
sphere, have their distinctness a maximum, when the sun 
sinks beneath the horizon. ‘The study of them, consequently, 
becomes exceedingly difficult in a climate where this luminary, 
even in a serene day, almost always sets in clouds; but as I 
have availed myself of every favourable moment for observa- 
tion, | have been able to execute a tolerably accurate delinea- 
tion of the atmospheric spectrum. 
It is a curious circumstance, that the atmosphere acts very 
powerfully round the line D, and on the space immediately on 
