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134 in taking place, there is an increase in the intensity of those already existing. The award then proceeds as follows: Thirteen years afterward Kirchhoff published his celebrated memoir on the relations between the coefficients of emission and absorption of bodies for light and heat, in which he established mathematically the same facts, and announced them as new.

We are, of course, aware that this is rather a burning question; but, whatever may be thought of the justice of these claims, there can be no doubt that the fact of their having been made on behalf of Dr. Draper by so distinguished a body as the American Academy of Arts and Science ought to be known, and that its judgment will receive at least respectful consideration whenever the early history of spectroscopic science comes to be written. And it is impossible not to draw attention to this fact in a notice, however brief, of Dr. Draper's volume; for, plainly, one of the motives of its publication is to assert his claims to priority of discovery in regard to the points above quoted. In fact, the four memoirs which bear 'directly on the subject of spectrum analysis are printed first in the volume, and are followed by a note in which Dr. Draper complains, though in very decorous language, that he has received considerably less than justice at the hands of M. Kirchhoff; and, by way of showing that he has tangible grounds for complaint, he makes the following quotations (p. 85) from M. Jamin's "Cours de Physique," in which results that he had previously established are formally attributed to M. Kirchhoff:

M. Kirchhoff has deduced the following important consequences:

Black bodies begin to emit at 977° Fahr. red radiations, to which are added successively and continuously other rays of increasing refrangibility as the temperature rises.

All substances begin to be red-hot at the same temperature in the same inclosure.

The spectrum of solids and liquids contains no fixed lines.

Now, it may be said with very little qualification that what is here attributed to M. Kirchhoff is to be found distinctly stated in the first memoir in the volume before us, which was published by Dr. Draper in 1847. By experimenting with a strip of platinum heated by the transmission of a current whose force could be regulated, he ascertained that the temperature at which red rays are first radiated is 977° Fahr. He also ascertained that platinum, brass, antimony, gas-carbon, and lead became incandescent at the same time with the iron barrel in which they were gradually heated, and that the apparent exceptions presented by chalk, marble, and fluor-spar were due to phosphorescence. By raising the temperature of the platinum wire and analyzing with a prism the light emitted, he proved that the length of its spectrum gradually increased with the temperature until at 2130° Fahr. the full spectrum of daylight was attained; and it is clear that he regarded the result thus obtained as being generally true. That the spectrum of the incandescent platinum contained no dark lines had indeed come out only incidentally in the course of the investigation; still it was not by any means a point seen but not observed; for, in consequence of observing it, he resorted to a comparison of the spectra of incandescent platinum at different temperatures with the spectrum of daylight in order to determine their extent, instead of fixing their extent by the dark lines of the spectra themselves, which he had ascertained to be non-existent. On the whole, the above statement breaks down at nearly every point. What is therein referred to M. Kirchhoff was certainly ascertained before by Dr. Draper. Whether Dr. Draper was the first person to observe all these points is a very different question, and one we would by no means prejudge; indeed, without going beyond the limits of the first Memoir, it is pretty plain that the temperature of incandescence was known with considerable accuracy before Dr. Draper's experiment with the platinum wire; and it certainly was believed (if not proved) that the temperature was the same for all bodies.

first edition of this work appeared