S2 On the Atomic Theory. 



their respective attraction being more or less powerful for that 

 element. Philosophers attribute it to their different degrees of 

 capacity for caloric ; this is merely expressive of the fact itself, 

 •without accounting for it. 



We 1\iiow that the particles of ponderable elements of various 

 kinds will unite to another imponderable element in different 

 proportions ; and in most cases, it is true, this does not depend 

 upon a superior force of affinity: — for example, an ultimate par- 

 ticle of azote will unite to more than twice the quantity of oxy- 

 gen that those of sulphur, phos]jhorus or carbon will ; yet the 

 latter substances have by far a more powerful attraction to oxy- 

 gen than the azote, for they will readily deprive it of all its oxy- 

 gen . probably this proceeds from the quantity of caloric or 

 electric matter which the compounds formed are capable of en- 

 gaging round their respective atoms *, Be the cause whatever 

 it may, it is a fact wliich I advanced twenty-nine years ago for 

 the first time, that the particles and atoms of ponderal)le matter 

 unite in various and definite proportions ; and the same law holds 

 good respecting the chemical union of caloric to bodies : — it unites 

 to some ponderable bodies in larger quantities than to others f. 



Every single ultimate particle of elementary matter, even in 

 solid masses such as metals, is surrounded with an atmosphere of 

 caloric. Caloric thus attached to particles comes under the de- 

 nomination of specific heat, and is no doubt intimately, if not 

 chemically, attached, as it does not affect our senses or the ther- 

 mometer. 



When two ultimate particles unite chemically, they come into 

 complete contact, and form one atom whose capacity for caloric 

 is less than its constituents in a separate or simple state ; hence 

 it is that caloric is liberated by chemical union. These atoms, 

 liowever, retain a sufficient quantity of caloric to furnish them 

 with atmospheres. 



When an atom, which consists of the most simple combina- 

 tion, unites to another atom chemically, the compound molecule 

 governs still less caloric than its constituent atoms ; yet that 

 molecule is enveloped with an atmosphere of caloric. Molecules 

 set bounds to chemical union ; molecules are as distinct or as 

 insulated from each other, notwithstanding their seemingly close 

 approximation in their liqtiid or solid state, as particles or atoms ; 

 or, comparatively, as the planets in our system in consequence of 

 their calorific atmospheres. 



Fluidity, flexibility, malleability, elasticity, and that vibratory 

 property which produces sound, dv^pend upon the internal struc- 



* All bodies naturally contain more or less electricity, but not in suffi- 

 cient quantity to disturb their light and caloric. 

 ■f See my Comparative View. 



ture 



