38 WRITINGS OF JAMES SMITHSON. 



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

 an hypothesis must be made, and its justness tried by a 

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

 the assumed hypothesis must be relinquished with candour 

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

 multitude of trials, invariably to accord with the results of 

 observation, as nearly as our means of determination au- 

 thorise 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 

 conversion of a substance into its several compounds, and 

 of these into one another, the simple ratios always obtain 

 which the principles of the theory require. Amongst the 

 multitude of instances which I could adduce, in support of 

 such being the fact, I will, for the sake of brevity, confine 

 myself to a few in the substances which have come under 

 consideration above, as they will likewise give the grounds 

 on which some of the proportions in the table have been 

 assigned, and every chemist, by a careful repetition of the 

 experiments, may easily determine for himself to what at- 

 tention the present theory is entitled. 

 Lead - - = f of sulphate of lead 



= |- of sulphuret of lead 

 Sulphuret of lead - = | of lead 



= -5^ of sulphate of lead 

 Sulphate of lead - = | of lead 



= f of sulphuret of lead 

 Antimony - - = i of powder of algoroth 



= f of sulphuret of antimony 

 Sulphuret of antimony - = V of powder of algoroth. 



In the experiments by which these relations were ascer- 

 tained, the portion of powder of algoroth and sulphate oi 

 lead dissolved in the precipitating and washing waters, was 

 scrupulously collected. 



