190 THEORY OF CONDUCTION. 



which contain less caloric around them in pro- 

 portion to their size, and being closer together, 

 attract and conduct it from one to the other, 

 with different degrees of rapidity ; modified by 

 the arrangement of their atoms, and perhaps by 

 other circumstances not yet fully understood. It 

 is, doubtless, owing to the crystalline structure of 

 ice, that it is a worse conductor of electricity 

 than water. May it not be owing to the same 

 cause that glass, resins, sulphur, and some other 

 bodies, are better conductors of electricity in the 

 liquid, than in the solid state ? 



That the conducting power of all bodies 

 augments in proportion as they are deprived of 

 caloric, may be regarded as a self-evident pro- 

 position. 



The conducting power of metals is increased 

 in proportion to their condensation by pressure, 

 for the same reason that it is augmented by a 

 reduction of temperature, that is, owing to the 

 loss of a portion of their latent caloric. Caloric 

 has a stronger attraction for pure metals than 

 for their oxides, chlorides, fluorides, bromides 

 and iodides ; their specific gravity, cohesion, and 

 conducting power are also greater. * 



* Lord Bacon observes, in the Second Book of the Novum 

 Organum, that it should be inquired why metals and stones, feel 

 colder to the living body than the fur of animals, silks, woollens, 

 feathers, wood, &c. ; whether the latter contain more inherent 

 heat than the former; and if so, whether it be owing to their 



