OF NATURAL PHILOSOPHY. 21 J 



would be ground for the logical objection of a vicious 

 circle : but this is not done ; the determination of 

 these numerical data is derived from experiments 

 purposely made on a great variety of different 

 combinations, among which that under consider- 

 ation does not of necessity occur, and all these 

 being found, independently of each other, to agree in 

 giving the same results, they are therefore safely as- 

 sumed as part of the system. Thus, the law of defi- 

 nite proportions, when applied to the actual state of 

 nature, requires two separate statements, the one 

 announcing the general law of combination, the 

 other particularizing the numbers appropriate to 

 the several elements of which natural bodies con- 

 sist, or the data of nature. Among these data, if 

 arranged in a list, there will be found opposite to the 

 element sulphur the number 16, and opposite to 

 lead, 104*; and since 20 is to 130 in the exact 

 proportion of 16 to 104, it appears that the com- 

 bination in question affords a satisfactory verification 

 of the law. 



(222.) The great importance of physical data 

 of this description, and the advantage of having 

 them well determined, will be obvious, if we con- 

 sider, that a list of them, when taken in combin- 

 ation with the general law, affords the means of 

 determining at once the exact proportion of the 

 ingredients of all natural compounds, if we only 

 know the place they hold in the system. In 

 chemistry, the number of admitted elements is 

 between fifty and sixty, and new ones are added 

 continually as the science advances. Now, the mo- 

 Thomson's First Principles of Chemistry. 

 P 2 



