PREFACE. Xi 



pace with the advancement of this moft im- 

 portant difcovery; and though neceflity was 

 the parent of the mechanic arts, yet they alfo 

 throve, and grevy to maturity, under the fame 

 influence. 



Many more inftances might be added to 

 this brief view of the utiHty of natural know- 

 lege ; but we fhall only give fome of its ufes 

 in the polite arts, which have hitherto been 

 too little conne(fled with it. 



To initance particularly in painting, its ufes 

 are very exteniive : the permanency of colors 

 depends on the goodnefs of the pigments ; 

 but the various animal, vegetable, and foflil 

 fubftances (out of which they are made) can 

 only be known by repeated trials ; yet the 

 greateft artifts have failed in this refped: the 

 fhadows of the divine Raphael have acquired 

 an uniform blacknefs, which obfcures the 

 lineft produdions of his pencil, while the 

 paintings oi Holbein^ Durer^ and the Venetian- 

 fchooly (who Vv'ere admirably fkilled in the 

 knowlege of pigments) ftill exift in their pri- 

 mitive freflmefs. 



But thefe advantages are fmall, compared 

 to thofe derived from the knowlege of nature 

 m the reprefentatioa of objects : painting is 



