SECOND REPORT— 1832 . 
272 
more heated part; whilst the heat would be thus more equally 
radiated to all parts of the second without such loss. 
Thus it appears that the fact stated by M. De la Roche is 
fully substantiated; while on the other hand it is satisfactorily 
accounted for, without supposing any new property of heat, or 
any direct radiation through glass. 
In some unpublished experiments of my own, I found upon 
observing the temperature acquired by a screen exposed to iron 
below luminosity, first plain, and then coated with Indian ink 
towards the source of heat, the thermometer being in contact 
at the central part on the outside, that it rose rather more on 
the plain , than on the coated screen . 
8. ) MM. Nobili and Melloni, in the Memoir before quoted, 
applied their instrument to estimate the effects of transparent 
screens. Over the thermo-multiplier were placed successively 
transparent screens of glass, sulphate of lime, mica, and of water, 
oil, alcohol, and nitric acid (inclosed between plates of glass ?), 
and also of ice. 
The source of heat was a ball of iron, heated to a point below 
luminosity, suspended, or rather passed rapidly, at a certain 
distance above the screen. 
The index indicated an instantaneous effect , greater or less 
in all cases except those of water and ice, in which none was 
produced, even when the iron was kept a longer time over the 
instrument, or even heated to redness, and the screen reduced 
in thickness. 
9. ) A set of experiments presenting some important results 
with respect to the absorbing and radiating properties of sur¬ 
faces, as well as the action of screens in air and in vacuo, are 
given by Mr. R. W. Fox, in the Phil. Mag. and Annals , New 
Series, No. 65, p. 245. A brief statement of the results is as 
follows: 
A cylindrical tin vessel of hot oil with its surface polished, 
and another similar, painted black, had their times of cooling a 
certain number of degrees observed under a receiver first highly 
exhausted, and then full of air ; the cylinders being respectively 
1st exposed, and 2ndly inclosed in one and sometimes more 
tin cases with intervals; the outer and inner surfaces being 
one or both polished or blackened. From all the different 
combinations of these results, of which he states in detail, I 
collect the following general inferences : 
I. In vacuo ; (1) the polished vessel had its cooling always 
accelerated by the cases ; and in this order— 
