Chap. 95] Colours of-opake Bodies. 273 



fleeted from the anterior furface. This diminution is 

 occafioned by the lofs of that part of the light which ia 

 abforbed in patting through the coloured glafs. 



The next object of this ingenious philotbpher was to 

 obtain the colouring particles pure and unmixed with 

 other media. To this end he reduced Feveral tranf- 

 parent coloured liquors to a folid confiftence by eva- 

 poration, and in this (late the colouring particles re- 

 flected fio light, but were entirely black. 



To determine the principle on which opake bodies 

 appear coloured, it is therefore only necefTary, in the 

 firft place, to recollect, that all the coloured liquors 

 appeared fuch only by tranfmitced light; and, adly, 

 that thefe liquors, fprcad thinly upon a white ground, 

 exhibited their refpedtive colours; Ke therefore con- 

 cludes, that all coloured bodies, which are not tranf- 

 parent, confift of a fubfcratum of fome white fub- 

 ftance, which is thinly covered with the colouring par- 

 ticles. 



On extracting carefully the colouring matter from 

 the leaves, wood, and other parts of vegetables, he 

 jjpund that the bads was a fubftance perfectly white. 

 He alfo extracted the colouring matter from different 

 animal fubftances; from flefli, feathers, &c. whence 

 the fame conclufion was directly proved; 



Flefh confifts of fibrous veflels-, containing blood, 

 and is perfectly white when divefted of the blood by- 

 ablution ; and the florid red colour of the fleih pro- 

 ceeds from the light which is reflected- from the -white 

 fibrous fubftance, through the red tranfparent covering 

 formed by the blood. 



The refult was the fame from an examination of the 

 mineral kingdom. 



Some portions of light are reflected from every fur- 

 face of a body, or from every different medium into 

 VOL. I. T \vhich 



