. SULPHURET OF LEAD, ANTITIIONY, AND COPPER. 335 



and it is not a little remarkable, that here, as was the case In sexagesimal 

 Vith the calamine*, they are sexagesimal fractions of it, ^^^cuons. 



When in a former paper I offered a system on the pro- 

 portions of the elements of compounds, I supported it by 

 the results of my oM'n experiments, which might be sup- 

 posed influenced, even unconsciously to myself, b)^ a fa- 

 vourite hypothesis, and I made the application of it prin- 

 cipally to a substance, the nature of which was not very 

 clear. But the present case is not liable to these objections : 

 here no fondness io the theory can be suspected of having 

 led astray, nor did even the experiments, a& they came 

 from their author's hands, bear an appearance in the least 

 favourable to it, and yet when properly considered, they 

 are found to accord no less remarkably Avith its principles. 



It is evident, that there, must be a precise quantity, in Elements of 



which the elements of compounds are united together jn '^^"^f"""'^'^. 



^ _ ^ = must unite m 



them, otherwise a matter, which was not a simple one, precise qaaa. 



would be liable, in its several masses, to vary from itself, '^^*^^''- 

 according as one or other of its ingredients chanced to pre- 

 dominate; but chemical experiments are unavoidably at- 

 tended with too many sources of fallacy for this precise 

 quantity to be discovered by them ; it is therefore to theory, 

 that we must owe the knowledge of it. For this purpose Hypothesis ne- 



an hypothesis must be made, and its justness tried by a ^^^^^^7 '^"'' 



•^ ^ 7 J . must be tested 



strict comparison with facts. If they are found at variance, by facts, 



the assumed hypothesis must be relinquished with candour 



as erroneous : but should it on the contrary prove, on 



a multitude of trials, invariably \o accord with ttie results 



of observation, as nearly as our means of determination 



authorise us to expect, we are warranted in believing, that 



the principle of nature is obtained ; as we then have all the 



proofs of its being so, which men can have of the justness 



of their theories; a constant and perfect agreement with 



the phenomena, as far as can be discovered. 



The great criterion in the present case is, whether on the Do the -:imple 



conversion of a substance into its several compounds, andJ^^'"- '^^/l"^'^^*^ 



, '^ ^ by the theory 



of these into one another, the simple rrttios always obtain, always obtain > 

 which the principles of the theory require. Amongst the 



* Phil. Trans. 1803^ p. 12. or Journal, vol VI, p. 83, 



flfiultitude 



