98 , j REPORT—1863, 
year 1831*, that snow shaded by trees, or generally by objects suspended 
from the ground, melted more rapidly than snow freely exposed to the radi- 
ating action of the sun or skies. To explain this apparently anomalous fact, 
Melloni thought it sufficient, in his commentst on a later paper by Fusinieri 
on the same subject+, to ascribe to snow a difference of absorptive powers for 
different rays, which he attempted also to prove by direct experiment. He 
denies that a conversion of light into heat—or, as we should more correctly 
express it, of Newtonic into Herschellic rays—can account for the effects ob- 
served, thinking the assumption to be disproved by the following experiment. 
The incidence of the rays emanating from some lamp produced in a thermo- 
electric pile § a current which, measured by the galvanometer attached, was 
equal to 15° when the rays passed freely through the air, but of 30°5 when 
the rays were first transmitted through a sheet of paper. When the rays were 
first of all transmitted through glass rendered opake by lamp-black, the re- 
sultant current was as 18°-19° to 10°-11°, according as the paper also was 
interposed or not. As the increase of calorific effect upon the interposition 
of the paper sheet thus occurred in the absence as well as in the presence of 
light—that is to say, of visible or Newtonic rays,—Melloni concludes that a 
conversion of the latter into heat—or, as we should say, into Herschellic rays 
cannot be the cause of the augmentation observed. This argument, however, 
as well as the explanation attempted by Melloni himself, is evidently falla- 
cious. To the latter, already Fusinieri very reasonably objected || that, since 
the direct beam issuing from a radiating source must necessarily contain all 
the rays to be found in the same after diffusion or reflection {]—besides, gene- 
rally, others,—the diffused or reflected beam could never offer to any substance 
more rays absorbable by it than the direct beam. On the other hand, Mel- 
loni’s experiment, so far from disproving the conversion of visible into other 
rays, tends rather to prove that, besides this conyersion, a transmutation of 
invisible rays also into others, probably of less refrangibility, is possible ; 
since the interposition of the paper sheet, in the absence of visible rays, still 
produced an increase of calorific action of 8°, against the 18°-5 which it caused 
in the presence of light**., As for Fusinieri’s own speculations on the subject, 
it is unnecessary to advert to them, since, besides not being clear, his expla- 
nation involves the materiality of rays, and proceeds from a negation of the 
discoveries of Melloni with reference to radiant heat. 
10. In 1861, Prince Salm called attention to Fusinieri’s observation, as 
the author of which he names Mellonitt. Without entering further into 
the matter, M. Salm considers the fact as proving the fluorescence of heat,— 
leaving it doubtful to some extent what the meaning is which he attaches to 
the expression. 
11. Induced by the above, M. Emsmann published in 1861 a note tt, in 
which he quotes a paragraph from an article contributed by him, in 1859, to 
* Annali delle Scienze, vol. i. p. 196. 
+ Comptes Rendus, vol. vi. p. 801 (1838). 
+ Annali delle Scienze, vol. viii. p. 38 (1838). 
§ It may be useful to mention that the exposed face of the thermo-electrie pile was 
covered with white-lead. 
|| Annali delle Scienze, vol. viii. p. 227. 
€{ Cases of ray-transmutation excepted, the occurrence of which Melloni strives to dis- 
rove. 
f ** Another instance in which the interposition of a screen produced an augmentation of 
ealorific effect was mentioned by Melloni, upon an earlier occasion, in Ann. de Chim. et de 
ae vol. ly. p. 387 (1834) Also Taylor’s Scientific Memoirs, yol. i. p. 68 (1837). 
t Pogg. Ann. vol. cxiii. p. 54 (1861). 
$t Pogg. Ann, vol. exiv. p. 651 (1861). 
