SCIENTIFIC MEMOIRS. 



VOL. I.— PART I. 



Article I. 



Memoir on the Free Transmission of Radiant Heat through 

 different Solid and Liquid Bodies ; jyresented to the Royal 

 Academy of Sciences of Paris, on the 4:th of February, 1833, 

 by M. Melloni. 



From the Annales de Chimie et de Physiqtie, t. liii. p. 1. 



IVIaRIOTTE was the first, so far as I am aMare, who attempted to 

 appretiate the action of diaphanous substances in transmitting or inter- 

 cepting the calorific rays which emanate from terrestrial sources. After 

 having observed that solar heat concentrated at the focus of a metallic 

 mirror, suffered no sensible diminution of intensity by being made to 

 pass through a glass plate, he took and placed his apparatus before the fire 

 of a stove, and found, that at the distance of five or six feet the tempe- 

 rature of the reflected image at the focus, when the rays were allowed to 

 meet there without impediment, was such as the hand could not bear ; 

 but that when the plate of glass was interposed there was no longer 

 any sensible heat, although the image had lost none of its brilliancy. 

 Whence he concluded that none *, or certainly but a very small portion, 

 of the heat of terrestrial fire passes through glass. 



About a century after Mariotte's time, the same experiment was re- 

 peated by Scheele, who, instead of imitating the cautious reserve of his 

 predecessor, asserted that from the moment when the glass was inter- 

 posed there was no longer any heat whatever at the focus of the mirror f. 



* Mariotte, Traite de la Nature des Couleurs ; Paris, 1686, part 2, at the 

 end of the Introduction. 



+ Scheele, Traili'del'Air et dn Feu ; Paris, 1781, §56. — The original work 

 of Scheele was published in 1777. Mariotte died in 1684. 



Vol. I. — Paut 1. n 



