M. Melloni on the Radiations of Incandescent Bodies, 
 rives with those that have been obtained by Wedgewood and 
Daniell, the difference is only 30° in excess for the first case, and 
3° too little in the second. The differences are much greater 
when compared with the deductions of Davy and Newton, 
which give 812° and 635°. But those numbers, and especially 
the latter, were obtained by methods too imperfect to be trust- 
worthy. Consequently, the number 977° EF’. given by our author, 
must approach very closely the degree of heat which produces the 
first incandescence of bodies. 
After having studied this first question, already examined by 
other philosophers, Professor Draper enters on an entirely new 
eld of research, investigating the nature of the colors which are 
deve eloped by an ignited body as its temperature is increas 
For this purpose he employed a prism of fine flint glass, setting 
it vertically at a certain distance from the strip of platina; but, 
previously, having placed in the position the platina was to oc 
cupy, a vertical slit of the same size in a piece of metal, Hips 
which a fais of the daylight passed. The spectrum resulting 
from the transmission of this beam through the prism was re- 
ceived on a small telescope furnished with micrometric wires, and 
carefully examined in its different parts, for the purpose of deter- 
mining exactly the position of F'raunhofer’s dark lines. The strip 
of ina was then set in the same place, and he proceeded to 
make observations on the spectra produced by it at different peri- 
ods of incandescence. [rom these it results that the first spec- 
trum visible in complete darkness corresponds to a pe aie of 
1210° EF. and extends from the fixed line B to the line The 
second spectrum produced by a temperature of 1325° commences 
very nearly at the same line B, and terminates at the line d; the 
third at a pis: paar of 1440°, appears to begin a little nearer 
the line A, and goes to some distance beyond G; lastly, the fourth, 
corresponding to a temperature of 2130°, approaches much nearer 
to A, and extends as far as the line /. In other words, the s 
trum of the strip of platina which corresponds to the red extremity 
of the prismatic spectrum, is at first very short, and contains only 
the less refrangible colors; but as the temperature rises, the spee- 
trum. of incandescence extenda towards the violet extremity, 
obtaining the more refrangible tints, and at last acquiring all the 
colors and all the extent of the solar spectrum, except the terminal 
rays at the two extremities, which escape the observer evidently 
on account of their pasos feebleness. The same cause (insen= — 
sibility due to a want of luminous energy) makes the first spec- 
trum appear, at the red end, a little shorter than the last ; because 
less refrangible rays of that color are, as is well known, so 
ren. in the solar spectrum, that we are unable to perceive 
ss they are isolated in a place that is totally dark. 
efore, ought they to remain inthe to bes ee 
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