SCIENTIFIC WRITINGS. 399 



spending to definite quantities of work, which have 

 been used up for constituting them. Only metallically 

 constituted bodies can enter into chemical combinations. 

 Latent heat therefore forms an obstacle to chemical 

 combination, and if such nevertheless occurs heat must 

 at the same time become sensible. Conversely a body 

 becoming chemically free must be constituted metalli- 

 cally, is therefore in the active state at the moment of 

 becoming free. Left to itself heat becomes latent by 

 absorption of sensible heat, if it is a semi- or non-metal, 

 whereby its electric conductivity is then partially or 

 wholly destroyed. Heightened temperature makes the 

 molecular arrangement, which corresponds to the heat 

 absorbed, less stable, enhances therefore the electrical 

 conductivity and at the same time the chemical affinity. 

 Since heat becomes latent when metals form alloys, the 

 conductive resistance of such alloys does not increase in 

 proportion to the absolute temperature, as with the 

 simple pure metals, but the latent heat of combination 

 of the alloy forms a disturbing element, which further 

 increases the resistance and thereby nullifies the pro- 

 portionality of the same to the absolute temperature. 



I succeeded in employing also technically the 

 metallically conductive modification II of crystalline 

 selenium, discovered by me, for the construction of 

 a selenium photometer. 



In an older paper I furnished the proof, that the 

 dielectric becomes heated by repeated charge and dis- 

 charge, and thereby found an experimental confirmation 

 of Faraday's molecular induction theory. 



