Pemanent Cvlours of Opake Bodies, 179 



ihck, when the tranfmitted light is intercepted, 

 or when the mafles are of a fufficient thicknefs. 



Several fruits and berries, as black cherries, 

 black currants, blackberries, and many others, 

 afford inftances of blacknefs arifing fronn the 

 denfc ftat«wof the colouring matter. Their 

 juices are red, when fpread thin on a white ground, 

 or otherwife viewed by tranfmitted light. 



Thus it appears, from all the preceding ex- 

 periments and obfervations, that Tranfparent 

 Coloured Matter, whether diffufed through co- 

 lourlefs pellucid media, or condenfed into folid 

 maffes, feparate and unmixed, is not endued with 

 any refledive power. 



I fliall proceed to confider the aftion, and pro« 

 perties, of the colouring particles of opake co- 

 loured bodies, and the means by which their 

 colours are produced. 



The tranfparent liquors and glaffes, which 

 have been already examined, owe their colours 

 to fuch particles extradted from opake fubftances : 

 and it has been fhewn that thofe particles do not 

 adl upon light by refledtion. 



It has alfo been obfcrved, that when coloured 

 particles are fpread thin upon any white ground 

 they exhibit their fcveral colours, by tranfmic- 

 ting the light reflt-fted from the white ground. 



I fhall endeavour to prove, by feveral experi- 

 ments and obfervations, that the colours of opake 

 bodies are produced by a fimilar operation. 



N 2 Amongft 



