292 
SECOND REPORT -1832. 
The exterior effect on the white bulb was in a much less ratio 
to that within the visible spectrum, than on the black. 
Sir H. Davy repeated these experiments in the clear atmo¬ 
sphere of Italy, and with thermometers of extremely minute 
size, to secure an instantaneous effect: he found the maximum 
beyond the red. 
These experiments were also tried by Ritter and by Prof. 
Wiinsch ( Magazin der Gesellsch, Sfc. Berlin 1807). He used 
prisms of different substances ; with alcohol, oil of turpentine 
and water, the maximum was in the yellow; with green glass, 
in the red; and with yellow glass, on the extreme boundary. 
3. ) But by far the most important and conclusive researches 
on this subject are those of Dr. Seebeck, wdio in a memoir read 
to the Royal Academy of Berlin, after discussing the conclusions 
and views of previous experimenters, proceeds to an elaborate 
series of experiments of his own, in which he has discovered 
the cause of all their discrepancies. The position of the maxi¬ 
mum heat in the spectrum depends entirely on the nature of the 
medium employed,—a circumstance almost wholly unnoticed by 
former experimenters. 
The heating intensity is very small towards the violet ex¬ 
tremity; it thence gradually increases in prisms of water, alco¬ 
hol, or oil of turpentine ; the maximum is in the yellow space: 
in those of solution of sal-ammoniac and corrosive sublimate, or 
sulphuric acid, it is in the orange; in crown glass and common 
white glass, in the middle of the red : in those glasses which 
contain much lead, it is in the limit of the red: and in flint glass, 
beyond the visible boundary, but nearer to it with Bohemian 
than with English glass. In all cases it gradually diminishes 
from the maximum, and is perceptible to some distance beyond 
the visible boundary. (Schweigger’s Neues Journ. x. 129; 
Annals of Phil. Sept. 1824; Abhandl. der Konigk. Acad. 
Wissenschaften in Berlin , 1818-19, p. 305; Phil. Mag. Nov. 
and Dec. 1825; Edinb. Journ. of Science , No. II. 358.) 
4. ) Analysis of the solar rays by the absorption of media. 
In respect to light, the remarkable variety in the absorption 
of different rays exhibited by different media has been well 
established, and affords a new sort of analysis of light. 
In regard to the solar heat, similar researches have been 
made, though as yet to little extent. The first observations of 
the kind were those of Sir W. Herschel (Phil. Trans. 1800). 
He found the absorption of several kinds of glass for his in¬ 
visible rays and for the middle red, to be proportional to the 
following numbers out of 1000 rays incident: 
