permanent Colours of Opake Bodies. i-8j 



Thefe means of tinging are fomewhat fimilar 

 to the application of vegetable dyes to linen, and 

 of tranfparent water colours to paper, manv of 

 which confift of the Colouring Matter of plants, 

 fuch as indigo, litmus, fap green, gamboge, 

 the vegetable lakes, and various others. 



Thefe operations are fo well known, and the 

 methods of executing them are fo obvious, that 

 I fhould not here have noticed them, if they had 

 not led me to fome obfervations refpefbing the 

 white grounds, on which the colours are ap- 

 plied. 



The confideration of thole white fubftances 

 affords much infight, into the manner in which 

 the natural colours of vegetables are produced. 



I have already (hewn that, when the Colouring 

 Matter of plants is extrafled from them, the 

 folid fibrous parts, thus diverted of their covering, 

 difplay that whitenejsy which is their diftinguilh- 

 ing charafter. 



White paper, and linen, are formed of fuch 

 fibrous vegetable matter j which is bleached, by 

 diflblving and detaching the heterogeneous 

 coloured particles. 



When ijiefe are dyed, or painted, with vege- 

 table colours, it is evident that they do not 

 differ, in their manner of ading on the rays of 

 light, from natural vegetable bodies: both 

 yielding their colours by tranjmitting through the 



N 4 Tranfparent 



