Permafient Colours of fake Bodies'. 157 



Nor were they enabled, on their return to 

 their own country, to transfer to it the methods 

 of executing thofe beautiful and magnificent 

 works, which had been the objedls of their ad- 

 miration. 



The moderns were not furnifhed with any 

 adequate means of retrieving the Principles of 

 ancient Science, till they began to avail them- 

 felves of experimental obfervations; and till 

 academies were inftituted, for the purpofe of 

 enabling them mutually to communicate their 

 djfcoveries to each other. 



The prefent age has produced many excellent 

 philofophers, whofe labours have been diredled 

 to inquiries, from whence great improvements 

 mud neceflarily refult to the Arts, and Opera- 

 tions, which are of the higheft importance to the 

 convenience and happinefs of mankind. 



Ifhall think my felf fortunate, if the flight ad- 

 dition of my endeavours prove, in the leaft de- 

 gree, conducive to that end. 



In a former work, I have confidered the Dif- 

 ferences or Changes of Colour, in permanently 

 coloured bodies, and have fhewn that they are 

 efFe6led in the fame manner, and according to 

 the fame law, which prevails in Tranfparent Co- 

 lourlefb Subftances. 



By this means, the pbilofophical principle is 

 cftabiin-ied, and applied to the pradical ufes of fe* 

 veral Arts ; particularly to thofe of Dying, Paint- 

 ing, 



