170 = =On the Production of Light by Chemical Action. 
with atmospheric air, constitute the oxydizing flame which en- 
velops the blue cone, ‘and emits Brewster’s monochromatic yellow 
light. ‘That the yellow — comes from this flame is proved by 
the greater length of its image. 
Vil. Physical cause of the production of light by chemical 
Wap 
not the various facts here brought forward, prove that all 
I combinations are attended by a rapid vibratory motion 
of the parts of the combining bodies, which intra become 
more frequent as the chemical action is more inten 
The burning particles which constitute the inner shell of a 
flame, are executing about four hundred billions of vibrations in 
one second; those in the middle about six hundred billions; and 
those on the exterior, in contact with the air, about eight hundred 
billions in the same time. The quality of the emitted light, as 
respects its color, depending on the frequency with which these 
vibrations are accomplished, increases in refrangibility as the vio- 
lence of the chemical action becomes greater. 
The parts of all material bodies are in a state of incessant vibra- 
tion. That which we call temperature, depends on the frequency 
and amplitude of those vibrations conjointly. If by any process, 
as by chemical agencies, we increase that frequency to between 
four and eight hundred billions of vibrations in one second, igni- 
tion or combustion result. In the case of the former of these 
numbers, the temperature is 977° F’. At this temperature or 
epoch, the waves propagated in the ether impress the organ of 
vision with a red light. This also is the temperature of the 
innermost shell of a flame. If the frequency of vibration still 
increases, the temperature correspondingly rises, and the light 
successively becomes orange, yellow, green, blue, &c., and this 
condition obtains in the successive strata of a flame, as we pass 
from its interior to its exterior superficies. 
The general principle at which I thus arrive, as the final result 
of this experimental investigation, viz., that there is a connexion 
between the vehemence with which chemical affinity is satisfied 
and the refrangibility of the resulting light, assumes the position 
of a simple consequence of the undulatory theory. Is it not very 
natural, if all chemical changes are attended by vibratory motions 
- the particles of the bodies engaged, that those vibrations 
crease in frequency or rapidity as the action becomes more vio- 
ig ? But an increased frequency of vibration is the same thing 
as an increased refrangibility. 
_ I think that, in this manner, the theory of ethereal undulations 
is on the point of including many of those fundamental facts in 
chemistry, which until now have been believed to be adverse to 
is or at all events as standing apart from it. the 
1ark that Mr. Whewell has made in his history of the In 
