YA yet : 
| * On the Refraction of Light. 359 
use lle 
sible coloric is indicated, and this, T have observed, not only in dif- 
ferently colorific rays, but in different rays of the same color: thus, 
by transmitting'a beam of red light through colored glass, and causing 
it to be refracted as in the foregoing experiment, it will be found, by 
a delicate thermometer, that the heat is greater at the base than at 
the summit of the image. The development of caloric* is, there- 
fore, directly as the density of the colorific rays. Now when a beam 
of white light is incident on a dense diaphanous medium of unequal 
_ thickness, such as the prism, its red rays, as they possess the greatest 
density, and hence penetrate glass with greater difficulty than the 
a. rays, are trajected through the thimest portion of the prism, 
Which they permeate with most facility. Having passed through 
less of the glass than their concomitant colors, they will consequently 
be less refracted, and occupy the base of the spectrum. The orange 
rays, being next in the order of density, pass through the next thin- 
hest portion of the prism, and having permeated a part of the glass, 
thicker than the red, and thinner than the yellow rays, they undergo 
m) 
n we introduce a pencil of red rays into a dark chamber through a plate 
* Whe 
of colored glass, the thermometer bein 2 placed in them, indicates a higher tempera- 
ture than in blue or violet light, admitted through colored glasses; but it would be 
E 
difference is owing to the circumstance of the calorific rays being less refracted 
by red than by blue glass, or that heat consists of differently refrangible rays. A 
gratuitous conclusion cannot easily be imagined; for what proportion exists 
between copiousness of heat and refrangibility? were the rays of caloric differently 
_ Tefrangible, why recur to glass prisms to prove it? or what analogy is there be- 
fach other. If the rays of caloric were differently refrangible, metallic prisms, 
i ularly silver ones, would answer the purpose of measuring the degrees of 
their refrangibility much better than glass ones, since they are much more perfect 
Conductors of coloric.t Far from having any proof that the rays of heat are gif- 
on 
vie w of ascertaining, whether the rays of heat, after passing 
through a conducting medium of metal, shaped like a burning glass, would converge 
toa focal point. A circular piece of glass was cut with a diamond, out of the mid- 
dle of a plane mirror, and in the hole was fixed a double convex lens 0 
€xactly fitted it. The mirror was mounted perpendicularly on a supporter, and an- 
+ Does the refrangibility depend on the conducting power? heat is hardly con- 
id 
ducted by water at all, solar heat instantly radiates through that fluid. 
Pe 
f silver which 
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