] 8 1 9 .] of the Theory of Heat. 195 



rather too small ; but on examining with attention all the correc- 

 tions which the authors were obliged to make on the immediate 

 results of their observations, it is easy to see that the rapidity 

 with which hydrogen gas cools down to the temperature of the 

 surrounding bodies, compared with other elastic fluids, ought 

 necessarily to introduce into the determination relative to that 

 gas an inaccuracy from which they did not attempt to free it. 

 By taking into consideration this cause of error, we are enabled 

 to explain the difference alluded to without being obliged to make 

 any forced supposition. 



The law of speciiic heats being thus established for elementary 

 bodies, it became very important to examine, under the same 

 point of view, the specific heats of compound bodies. Our pro- 

 cess applying indifferently to all substances, whatever be their 

 conductibility or state of aggregation, we had it in our power to 

 subject to experiment a great many bodies whose proportions 

 may be considered as fixed ; but when we endeavour to mount 

 from these determinations to that of the specific heat of each 

 compound atom by a method analogous to that which we 

 employed for the simple bodies, we find ourselves soon stopped 

 by the number of equally probable suppositions among which we 

 must choose. If the method of fixing the weight of the atoms 

 of simple bodies has not yet been subjected to any certain rule, 

 that of the atoms of compound bodies has been, a fortiori, 

 deduced from suppositions purely arbitrary. But instead of 

 adding our own conjectures to those which have been already 

 advanced on the subject, we choose rather to wait till the new 

 order of considerations which we have just established can be 

 applied to a sufficiently great number of bodies, and in circum- 

 stances sufficiently varied that the opinion adopted may be 

 founded on decisive conclusions. We shall satisfy ourselves with 

 saying, that in abstracting every particular supposition, the obser- 

 vations which we have hitherto made tend to establish this 

 remarkable law ; viz. that there always exists a veiy simple ratio 

 between the capacity of the compound atoms and that of the 

 elementary atoms. 



We may likewise deduce from our researches another very 

 important consequence for the general theory of chemical actions, 

 that the quantity of heat developed at the instant of the combi- 

 nation of bodies has no relation to the capacity of the elements; 

 and that in the greatest number of cases this loss of heat is not 

 followed by any diminution in the capacity of the compounds 

 formed. Thus, for example, the combination of oxygen and 

 hydrogen, or of sulphur and lead, which produces so great a 

 quantity of heat, occasions no greater alteration in the capacity 

 of water or of sulphuret of lead than the combination of oxygen 

 with copper, lead, silver, or of sulphur, with carbon, produces in 

 the capacity of the oxides of these metals, or of carburet of 

 sulphur. 



N2 



