NATURAL PHILOSOPHY. 141 



IDENTITY OP LIGHT AXD HEAT. 



MELLON i lias just published, at Naples, and presented to the French 

 Academy, on May G, the first part of a work entitled " La Thcrmo- 

 crose, on la Coloration Calorifiqiie," the object of \vhich is to show 

 that the luminous and calorific rays possess the same heterogeneous 

 constitution, proceed from one agent only, and from a single scries of 

 radiations, part of \vhich affect the organs of vision, whilst the other arc 

 revealed to our senses only by phenomena which accompany the heat- 

 ing of bodies. In short, that rays of heat are distinct in kind and prop- 

 erties, like the rays of different colors, which, differing in refrangibil- 

 iiy, compose white light. 



Transmissibility of Hcot. A paper was presented to the French 

 Academy on July 8th, by Messrs. Masson and Jamin, " On the trans- 

 missibility of heat/' The object of their researches was to examine 

 two theories of heat. whether heat and light are the effects of differ- 

 ent causes, or whether they are two different effects from a single cause ; 

 and to tbis end they repeated and extended the experiments of Melloni. 

 The two most interesting points were the extinction of the dark rays of 

 a solar spectrum by glass and by water, as stated by Melloni ; and the 

 calorific spectrum passing through fflass of cobalt-blue, not presenting 

 any alternations similar to the bright and dark bands of the solar spec- 

 trum so treated. Messrs. Masson and Jamin do not find heat extin- 

 guished by its transmission through glass or water ; and they do find 

 the same bands for heat as for light passing through blue glass. In 

 short, they show that colorific and calorific extinction or transmission 

 follow the same laws ; moreover, they also show that the relation of 

 the quantities of light and heat transmitted to the direct quantities is 

 always identical, and that the speed and length of a wave of heat are 

 also identical with those of light. Their results seem to warrant the 

 following conclusions. 1. In all phenomena produced by a radiation 

 of the same refrangibjlily, calorific and luminous, the relations of the 

 quantities of heat and light before and after being acted upon are iden- 

 tical. 2. All vibrating modifications established in the case of light 

 are found again, with the same intensity and the same numerical value, 

 in the case of heat. This constant proportion in the effects is sufficient 

 to prove the identity of causes. 



Some observations communicated at the same time by Provostaye 

 and Desains, " On the polarization of heat by simple refraction," go to 

 confirm the above view, that the laws of radiating heat are precisely 

 tliose of light. In regard to intensities, the numerical values are fre- 

 quently the same in the two cases, provided rays the same in origin 

 and refrangibility be used. 



Moigno and Matteucci have noticed another fact connected with this 

 question. In all cases the negative pole of a voltaic battery or pile be- 

 comes luminous previous to the completion of the electric arc, and is 

 relatively much colder than the positive pole. Hence it is inferred 

 that lijzht is developed in virtue of some peculiar function of the nega- 

 tive pole of the battery, independent of the process of combustion 

 which constitutes the phenomenon of the ordinary electric light ; and 



