On the Production of Light by Chemical Action. 165 
This being understood, I may illustrate the facts now to be 
brought forward by an example of the prismatic analysis of a 
horizontal element of the flame of a spirit-lamp—it being under- 
stood that the prism is at its angle of minimum deviation, and 
the spectrum seen through the telescope. All the prismatic col- 
ors in their proper order are visible, the sides of the spectrum 
not being parallel, the inclination being quite rapid toward the 
red extremity, the rays of which come from the interior of the 
ame where the diameter is less. Mere inspection is sufficient 
to show the rapid approach of the red sides to each other ; and 
I satisfied myself that, even in the more refrangible regions, there 
is the same want of parallelism, by rotating the telescope on its 
vertical axis, so that the vertical wires in its eye-piece might co- 
incide with first one and then the other side of the spectrum. 
It will be understood that I took the proper precautions not to be 
deceived by a partial want of achromaticity in the telescope, 
which might have led to a mistake. 8 
But further, the yellow space of such a spirit-flame spectrum 
is crossed by a bright fixed line, Sir David Brewster’s monochro- 
matic ray. It is a beautiful example of the principles just point- 
ed out in this method of horizontal analysis, being of much great- 
er width than the rest of the spectrum, and recalling to the imag- 
ination the appearance of Saturn’s ring when nearly closed, and 
seen through a telescope of moderate power. This ray, from its 
Superior breadth, must necessarily come: from that pale tawny 
light which invests the bright part of the flame. This, which is 
readily seen when the flame is large, envelops the middle and up- 
per parts, but cannot so easily be detected low down. It is to be 
attributed to the carbonic acid and steam that have risen at a high 
temperature in the burning shell, and are escaping at a degree 
above that of incandescence into the air, and are mingled wit 
oxygen diffusing from the air into them. A similar tawny cloak 
surrounds the upper part of the flame of a candle; it answers to 
the oxydizing flame of the blowpipe, and yields Brewster’s mo- 
hochromatic yellow light. . ; 
Ay. Dapbeccin: of the nature of colored flames ; shewing Jor 
example, why carbonic oryd burns blue, and cyanogen gas rg 1 
To return now to carbonic oxyd and cyanogen: fig. 1, No. 1, 
Tepresents the solar spectrum with its fixed lines ; No. 3 represents 
the spectrum of carbonic oxyd burning in the air. It begins in 
the red region, short of the fixed line C, and terminates agate 
the lines G and H. It yields therefore rays of every color, 
is is in accordance with the principles I have laid down. But 
when the relative quantity and force of the rays is estimated, in 
comparison with the sun light spectrum, the red aud orange are 
deficient, and the more refrangible colors predominate, and indeed 
it is the excess of these that gives the flame its characteristic blue 
