203 
Account of the Remains of a Fossil Extinct Reptile recently dis- 
covered at Haddonfield, New Jersey. 8vo . — From Dr I. 
Lea. 
Proceedings of the Royal Medical and Chirurgical Society of London, 
Yol. III., Part I. 8 vo . — From the Society. 
Journal of the Asiatic Society of Bengal. No. 269. 8vo . — From 
the Society. 
Monday . 18 tli April 1859. 
Professor CHRISTISON, Vice-President, in the Chair. 
The following Communications were read : — 
1. Researches on Radiant Pleat. Part II. By Balfour 
Stewart, Esq. Communicated by the Secretary. 
The first part of this paper describes the following groups of ex- 
periments : — 
I. On the effect which roughening the surface of a body pro- 
duces upon its radiation. 
II. On the nature of that heat which is radiated by rock-salt at 
at 212° F. 
III. On the radiation of glass and mica at high temperatures. 
The second or theoretical portion of the paper has reference to 
the law which connects the radiation of a particle with its tempera- 
ture, and to Dulong and Petit’s experiments on this subject. The 
instruments used, and method of using them, were almost the same 
as described in the first series of these researches. 
With regard to the first group of experiments, it was ascertained 
that roughening surfaces of glass or rock-salt with emery paper 
until they are dim for light, neither alters the quantity nor the 
quality of the heat which they radiate ; the surface, although dim for 
light, being yet specular for heat. 
With regard to the second group of experiments, it was shown 
that heat from rock-salt at 212° F. penetrates a screen of glass or 
mica less easily than lamp-black heat at 212° F. 
It also penetrates a screen of mica split by heat less easily than 
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