INTRODUCTION 15 



discovering the Philosopher's Stone, capable of converting everything 

 into i^'old and diamonds, and of making the old young again. This 

 solution of the question was afterwards most decidedly refuted, but it 

 must not, for this reason, be thought that the hopes held by the 

 alchemists were only the fruit of their imaginations. On the contrary, 

 the first chemical experiments might well lead them to their conclusion. 

 They took, for instance, the bright metallic mineral galena, and they 

 extracted metallic lead from it. Thus they saw that from a metallic 

 substance which is unfitted for use they could obtain another metallic 

 substance which is ductile and valuable for many uses in the arts. 

 Furthermore, they took this lead and obtained silver, a still more 

 valuable metal, from it. Thus they might easily conclude that it was 

 possible to ennoble metals by means of a whole series of transmutations 

 that is to say, to obtain from them those which are more and more 

 precious. Having got silver from lead, they only aimed at getting gold 

 from silver. The mistake they made was that they never weighed or 

 measured the substances used or produced in their experiments. Had 

 they done so, they would have learnt that the weight of the lead was 

 much less than that of the galena from which it was obtained, and the 

 weight of the silver infinitesimal compared with that of the lead. Had 

 they looked more closely into the process of the extraction of the silver 

 from lead (and now silver is chiefly obtained from the lead ores) they 

 would have seen that the lead does not change into silver, but that it 

 only contains a certain small quantity of it, and this amount having 

 once been separated from the lead it cannot by any further operation 

 give more. The silver which the alchemists extracted from the lead 

 was in the lead, and was not obtained by a chemical change of the lead 

 itself. This is now well known from experiment, but the first view of 

 the nature of the process was very likely to be erroneous. 23 The 

 methods of research adopted by the alchemists could not but give little 



23 Besides which, in the majority of cases, the first judgment on most subjects which 

 do not repeat themselves in everyday experience under various aspects, but always in one 

 form, or only at intervals and infrequently, is usually untrue. Thus the daily evidence 

 of the rising of the sun and stars evokes the erroneous idea that the heavens move and 

 the earth stands f^fcill. This apparent truth is far from being the real truth, and is even 

 contradictory to it. Similarly, an ordinary mind and everyday experience concludes that 

 iron is incombustible, whereas it burns not only as filings, but even as wire, as we shall 

 afterwards see. With the progress of knowledge very many primitive prejudices have 

 been obliged to give way to true ideas which have been verified by experiment. In ordi- 

 nary life we often reason at first sight with perfect truth, only because we are taught a 

 right judgment by our daily experience. It is a necessary consequence of the nature of 

 our minds to reach the attainment of truth through elementary and often erroneous 

 reasoning and through experiment, and it would be very wrong to expect a knowledge of 

 truth from a simple mental effort. Naturally, experiment itself cannot give truth, but it 

 gives the means of destroying erroneous representations whilst confirming those which 

 are true in all their consequences. 



