176 NOTICES OF THE MEETINGS [April 23, 
wave-theory present an irresistible accumulation of proof of the 
identity of the rays of heat with a succession of waves in an etherial 
medium: exhibiting different properties in some dependence on their 
wave-lengths. 
Among the most recent researches on the subject are those of 
Mr. Knoblauch (of which a translation is given in Taylor’s Foreign 
Scientific Memoirs, Part xviii. and xix.) and they are not to be sur- 
passed for extent and accuracy of detail. 
One series is devoted to the examination of the alleged differences 
in radiation of heat proportioned to the temperature of the source. 
This as before observed is an untenable hypothesis, but Mr. Knob- 
lauch distinctly refutes it by a series of experiments on alcohol flame, 
red hot metal, hydrogen flame and an argand lamp, whose tempera- 
tures are in the order of enumeration beginning with the highest : 
but the power of their heat to penetrate screens is found to follow 
exactly the reverse order. And even with lower stages of heat, the 
effects bear no proportion to the temperatures as such. Hence the 
effect is evidently not due to a mere extrication of the heat of tem- 
perature, but is of a peculiar kind. In a word, agreeably to the pre- 
ceding remarks, the different species of rays, more or less compounded 
together in the several cases, exhibit their diversities of character in 
developing heat by their absorption. One very peculiar result is, 
that Platinum, at a stage intermediate between red and white heat, 
transmits through all the screens employed rather less heat than 
when at a red heat. That is, these intermediate rays are of such a 
wave-length as to be subject to a peculiar absorption by these screens : 
while at the same time possibly less of the former may be emitted. 
In another section Mr. Knoblauch adverts to the effects of sur- 
faces on the absorption of rays, and particularly remarks (p. 205) ; 
*« The experiments of B. Powell and Melloni have shewn that one 
** and the same body is not uniformly heated by rays from different 
** sources, which exert the same direct action on a blackened thermo- 
** scope ;” a statement which does not very intelligibly express any 
conclusion of the author’s. Mr. Knoblauch however supports it by 
elaborate experiments shewing, as might be anticipated, that an ar- 
gand lamp affects a surface of carmine less, and one of black paper 
more, while a cylinder heated to 212° affects the carmine more and 
the black paper less. 
Another extensive series, on the effect of surfaces on radiation, is 
directed to shew that the effect is independent of the source whence 
the heat so radiated, was originally obtained. 
Among the very multifarious results referring to screens and sur- 
faces obtained by Mr. Knoblauch, it can here only be remarked that 
none of those varied facts appear to present anything at variance 
with the principles here advocated, while in the general conclusions 
which he indicates at the close of his memoir, the author though 
professedly avoiding all hypothesis, yet distinctly intimates his con- 
viction of the heterogeneity of the heating rays increasing as the 
condition of the source rises inthe scale from a low heat up to lumi- 
