and on the Elementary Colors of the Solar Spectrum. 
This parallel march of the two agents seems to have entirely ’ 
changed the opinion of the author as to the nature of the rays of 
light and heat, and the different chemical and physiological effects 
due to the sun and terrestrial luminous and calorific sources. 
The preamble of his memoir contains the following passage rela- 
tive to this point: 
“As the experiments now to be described lead to some striking 
and perhaps unexpected analogies between light and heat, they 
commend themselves to our attention, as having a bearing on the 
question of the identity of those imponderable principles. It is 
known that heretofore I have been led to believe in the existence 
of cardinal distinctions, not only between these but also other 
imponderable agents; and I may therefore state, that when this 
investigation was first undertaken, it was in the expectation that 
it would lead to results very different from those that have actu- 
Yy arisen.” 
. The author adds, immediately after the experiments relative to 
the luminous and calorific radiations, which are simultaneously de- 
veloped in the strip of platina at different phases of incandes- 
cence, “I cannot here express myself with too much emphasis 
on the remarkable analogy between light and heat which these 
experiments reveal. The march of the phenomena, in all their 
leading points, is the same in both cases. The rapid increase of 
effect as the temperature rises is common to both. And it is not 
to be forgotten, that, in the case of light, we necessarily measure 
its effects by an apparatus which possesses special peculiarities. 
The eye is insensible to rays which are uot comprehended within 
certain limits of refrangibility.. In these experiments, it is requi- 
site to raise the temperature of the platinum almost to 1000° be- 
fore we can discover the first traces of light. Measures obtained 
under such circumstances are dependent on the physiological ac- 
tion of the visual organ itself, and hence their analogy with those 
obtained by the thermometer becomes more striking, because we 
should scarcely have anticipated that it could be so complete.” 
After the second series of experiments, relative to the quality 
of the rays emitted as the temperature of the metal rises, Profe: 
sor Draper criticises some of the facts upon which Sir D. Brews- 
ter founds his opinion on the existence of the red, yellow and 
blue colors in every part of the Newtonian spectrum. ‘1 hese crit- 
cisms acquire more importance sivce the illustrious mathemati- 
cian, Airy, the Astronomer Royal of England, has denied the de- 
ductions of Sir D. Brewster, and refers to several of his experi- 
mental researches in support of the view, we a particular color 
serted in the num 
ith Pee Day Mr me 
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