350 
REPORT— 1854. 
The author considers that these distinctions fully account for the observed 
phenomena. 
Upon this we may observe,— 
The investigation cannot with correctness be called one on the transmis¬ 
sion of “ radiated heat" in general; it is restricted to that peculiar form or 
case of radiation which is manifested in the solar rays, and proves nothing 
as to the radiation from hot bodies, or even that conveyed in the rays from 
artificial lights, unless, as iuferred, by analogy. All the differences observed 
depend simply on the unequal absorption of the rays of light by the crystals 
and the coloured glasses. 
Melloni’s recent Experiments. 
In the ‘ Comptes Bendas,’ No. JO, p. 4-29, March 6,1854, Melloni gives 
some brief remarks in reply to certain objections raised by MM. Provostaye 
and Dcsains against the accuracy of experiments with the thermo-multipHer 
on the passage of heat through screens. 
lie points out as the sources of discrepancy, the ob/u/ue passage of the revs 
through a thick diathermanous screen, which is greater or less according 
the distance, and gives different effects of internal reflexion and absorption 
in different cases. 
To show that the errors objected arise solely from this source, he desc— 
a careful repetition of his experiments in which it was guarded against. 
The series of experiments included the usual set of sources, viz. 
00 The flame of on oiMarap; 
(2.) Incandescent plutina kept up by vapour of alcohol; 
Id.) Plate of copper heated by lump ; 
00 Vessel of hot water. 
Equalizing the effects on the thermo-multiplier by changing the distance 
and interposing a rock-salt screen, the diminution of effect appeared the 
same for the first three sources, but greater for the fourth. 
But this last result he contends was simply due to the greater proximit) 
of the source, and consequent greater differences of inclination of the ray;, 
and when equalized in this respect, the difference in nuestion disappeared, or 
might even be reversed. 
In the same notice Melloni refers briefly to other results which have bee 11 
obtained by means of rock salt. 
(1.) Jhat with a prism of rock salt the maximum of calorific effect in the 
solar spectrum is thrown further from the limit than with other 
tnermochroiques. 
the radiation from the sun diminishes from the centre to the 
r“ ereUCe ; i \ ,at t,,e radiatio » from the spots is less than from the resle 
wL B “„^“tyM;w,- qUa,0ri01 reSi ™ ° f the *"*" ‘ kf 
“ t'L'Z t0 ,hat 1 b «« informed that in a wort enti&J 
.rtat modi&dtil n°t Jong since published at Naples, AI. Melloni has «*r 
trine of the id m f !“T opmions, and seems disposed to assent to the 
according st,! ? ° f tbe ' “ ! ' a » h '<* produce light and heat, or heat ah*! 
.om/of is fo™ 1 "' B ,t r S tor , ) vave "iength; and I,a! explained and r*»fj 
more pUiset™;„;! ,ffiOUU ' C ' S ' 1 ‘^ Kt t0 be «-»• al l** - “ 8 ' 
efforts' tetUT i , , ; , ' ormcd . Iias b «# led to admit that the cbt*^ 
teristic of peihaT^e Jer^hs™ 1 ' Se ‘ ° f r “ yS ’ diff<!ring °"' J " 
°lc, the question of the evidence for and against this theory it 
