the conducing Poiver of Bodies. 531 



Let M be a body (a mafs of iron for inftatice) compofed of X 



an indefinicc number of particles, arranged in tbe ftrata i— — — ^ 



I, 2j 3, 4, 5, 6, 7, &c. Let caloric be communicated to it in 2 > ■ 



the dire£iion X. The firft ftratum of particles i combines with 3 ' 



R certain dofe of this caloric, and forms a compound, which 4 ■ ■ M 



we (hall call A. This compound Cannot be decompofed by the 5 



fecond ftratum, becaufc all the ftrata, before the application of 6 — 



the heat, were at the fame temperature; confequcntly, the 7 



affinity of all for caloric muft have been equal. Now it would be abfurd to fuppofe a 

 compound deftroyed by an affinity not greater than that which produced it. If, therefore, 

 only one dofe of caloric combined with ftratum i, no caloric could pafs beyond that ftratum. 

 But the compound A has ftill an affinity for caloric ; it therefore combines with another 

 dofe of it, and forms a new compound, which we fhall call B. Now It is a general law, 

 to which I know not a fingle exception, that when a body combines with different dofes 

 of another body fucceffively, the firft dofe is retained by a ftronger affinity than the fecond, 

 the fecond by a ftronger than the third, and fo on. Thus iron, by combining with 2^ 

 per cent, of oxygen, forms the green oxide of iron : by combining with 48 per cent, it 

 forms the brown oxide. Here, then, are two dofes of oxygen which combine fucceffively 

 with the iron ; the firft is 28 per cent, the fecond 23 per cent. Now the fecond dofe is 

 not retained by an affinity nearly fo great as the firft dofe. For many fubftances are 

 capable of abftrafting the fecond dofe, and, confequcntly, of converting brown oxide of 

 iron into green oxide which have no aftion on the green oxide : but all the bodies 

 capable of decompofing the green oxide are capable alfo of decompofing the brown ■ 

 oxide. 



Let us apply this general law to the componud B, into which ftratum i has entered. 

 This ftratum is now combined with two dofes of caloric, the firft of which is retained by a 

 ftronger affinity than the fecond. Stratum 2, therefore, though incapable of decompofing 

 the compound A, has a ftronger affinity for caloric than compound A has for the fecond 

 dofe of caloric ; it therefore felzes upon this fecond dofe, combines with it, and forms 

 the compound A. Here, now, are two ftrata of particles, combined each with a dofe of 

 caloric, and, confequcntly, conftltuting the compound A. The third ftratum is unable to 

 decompofe the fecond, for the fame reafon that the fecond was unable to decompofe the 

 firft. Stratum 1 again combines with a dofe of caloric, and forms compound B : ftratum 2 

 is unable to decompofe this componnd, becaufe being already compound A, its affinity for 

 caloric cannot be greater than that of compound A. Caloric, then, cannot pafs farther 

 through the body; but ftratum i combines with a new dofe of caloric, and forms a com- 

 pound, which we fhall call C. The affinity of this third dofe being inferior to that of the 

 fecond, ftratum 2 dccompofes compound C of ftratum i, and forms itfelf compound B. 

 This compound is decompofed by ftratum 3, which now forms compound A. Stratum 1 

 again forms compound C, which is again decompofed by ftratum 2, which ftratum forms a- 



3 Y 2 HCW 



