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and on the Elementary Colors of the Solar Spectrum. (13 
that Sir David Brewster is the author of very many beautiful 
and important discoveries confirmed by experiment ;—works, 
from which the conclusion here arrived at, can never detract their 
erit; any more than the errors committed by Newton on. dif- 
Jraction and the dispersion of luminous rays by diaphanous bodies 
of different kinds, can ever lessen the glory which must belong 
to his optical researches, and his discovery of the system of the 
; universe. 
To return to the researches of Professor Draper. 1 say that 
they conduct, as do others heretofore known, on light and radi- 
ant heat, to a perfect analogy between the general laws whic 
govern these two great agents of nature. I will add, that I re- 
gard the theory of their identity as the only one admissible by 
the rules of philosophy; and that I consider myself obliged to 
adopt it until it shall have been proved to me that there is a ne- 
cessity of having recourse to two different principles for the ex- 
planation of a series of phenomena which at present appear to 
me to belong to a solitary agent. 
_ Iconelude, that the molecules of bodies, slightly heated, vibrate 
slowly, and produce long and invisible waves in the ethereal me- 
dium which surrounds them. As the temperature rises the mole- 
cular vibrations chiefly augment in extent, preserving the same 
isochronism; but some among them increase in frequency also. 
This increase, nevertheless, does not become very distinct until 
near the point of incandescence. Then a portion of the ponder- 
able particles commence to vibrate more swiftly than the rest, 
and produce in the ether shorter undulations, which are conse- 
quently more refrangible ; and of which some become visible ; 
all contributing to increase the energy and variety of the radiation, 
until at last a great number of elements of luminous and obscure 
heat are found united in the radiant flux from sources of high 
temperature.* ; 
_ There are, however, certain bodies whose state of molecular 
equilibrum is such that their particles possess a great facienal 
ae 
Vibration ; these particles acquiring long before the period. 
candescence, altogether or partly, that rapidity of oscillation from 
ese views, being the direct consequences of the undulatory cg de - 
established in the memoir of Professor Draper here reviewe ‘ 
nt, but also in an earlier pa serted in the Philosophica am se Feb., 
a translation is given in the Biniebiany es gy + is : bic 
troductor 
Fespecting which M se bro semiaciy mer cue bisrifaite et Paishcatton a 
uable qu'il contient des phenoménes si singuliers de l’anta ray 
effets chimiques.”’ It also ap from t er, that he 
ars f He 
Id them ever since 1842, and used them for the purpose of explaining those 
of chemical interference which Sir J. Herschel describes, on the 
sis that the e waves cause the particles of surfaces on whic y 
Note of the Translator.) 
