60 NATURAL HISTORY. 



be better inquired : and the quantity of the fifteenth 

 turned to a twentieth : and likewise with some little 

 additional, that may further the intrinsic incorporation. 

 Note that silver in gold will be detected, by weight 

 compared with the dimension; but lead in silver (lead 

 being the weightier metal) will not be detected, if you 

 take so much the more silver as will countervail the 

 over-weight of the lead. 1 



Experiment solitary touching fixation of bodies. 



799. Gold is the only substance which hath nothing 

 in it volatile, and yet melteth without much difficulty. 

 The melting sheweth that it is not jejune, or scarce in 

 spirit. So that the fixing of it is not want of spirit to 

 fly out, but the equal spreading of the tangible parts, 

 and the close coacervation of them : whereby they 

 have the less appetite, and no means at all to issue 

 forth. It were good therefore to try, whether glass 

 remolten do leese any weight ? for the parts in glass 

 are evenly spread ; but they are not so close as in 

 gold ; as we see by the easy admission of light, heat, 

 and cold ; and by the smallness of the weight. There 

 be other bodies fixed, which have little or no spirit ; 

 so as there is nothing to fly out ; as we see in the 



1 It is strange that Bacon should not have seen that by taking away 

 more silver you diminish the dimension. The only way in which an alloy 

 of lead and silver could escape detection by the test used by Archimedes, 

 or at least by more exact methods of the same kind, would be to make 

 some part of the work hollow. But if this was Bacon s meaning, he has 

 not expressed it. It is yet more strange, the intention of the experiment 

 being to effect a saving of the precious metal, that he should have spoken 

 as if turning a fifteenth into a twentieth were an improvement. But per 

 haps he meant to make detection yet more difficult. We may remark 

 farther, that all gold in common use contains more than a fifteenth of alloy. 

 The money standard of England, which is above the average of continental 

 coinages, contains one part of alloy to eleven of fine gold. 



