178 NOTICES OF THE MEETINGS. [April 23, 1852; 
They are all more or less capable of exciting heat when absorbed 
or stopped: though in some the effect is perhaps insensible. Both 
this property and that of their transmissibility seems to depend in 
some way on the wave-length, though in no simple ratio to it. 
The absorptive effect due to ¢exture of surfaces has some direct 
relation to the magnitude of the wave-length, especially near the 
limit. While that due to darkness of colour is connected with 
shorter wave-lengths such as belong to rays within the limits of the 
light spectrum: and in any case when a ray impinges on any absorb- 
ing substance, its vibrations, being stopped, communicate to the mole- 
cules of the body vibratory movements of such a kind as constitute 
heat of temperature. 
The peculiar molecular constitution of bodies which determines 
their permeability or impermeability to rays of any species, gives 
rise to all the diversities of effect, whether luminous or calorific. 
We thus escape all such crude ideas, at once difficult and unphiloso- 
phical, as those either of two distinct material emanations producing 
respectively heat and light, or of a conversion of one into the other ; 
and obtain a view far more simple and consistent with all analogy. 
[B. P.] 
In the Library were exhibited : — 
Dr. W. B. Herapath’s Iodine of Disulphate of Quinine (a crystalline 
substance which has the power of Polarizing a ray of Light like 
a tourmaline. [Exhibited by Col. P. J. Yorke, M.R.I.] 
Specimen of Decorative Drawing (by a Lady). [Exhibited by C. 
B. Mansfield, Esq., M.R.I.] 
Specimens of Carving in Wood, by Mr. W. G. Rogers. 
Wire Models illustrating Geometry, Crystallography, &c. [Exhibited 
by Mr. Tennant.] 
Plan of Battle at Borodino — Nelson’s hat — Antique Military Ac- 
coutrements, &c. [From The United Service Institution. ] 
Ancient sword of State formerly carried before the Bishop of Treves. 
[Exhibited by Messrs. Hunt and Roskell.] 
