Permanent Colours of Opake Bodies. 245 



tervals which intercede the Opake Particles dif- 

 fufed through them. For, when the Opake 

 Particles are fo denfely arranged, that they inter- 

 fe£t, and cover, the interftices which lie between 

 thenn, the pafTage of the rays is obftrucled, and 

 none of them are tranfmitted : but, the mafs 

 ceafes to be femipellucid, and becomes opake. 



The fame caufe of obftruftion to the pafiage 

 of the rays takes place in Tranfparent Coloured 

 Bodies, when the Colouring Particles are denfely 

 arranged : fo that the light is intercepted and 

 abforbed, by the colouring matter, and the mafs, 

 confequently, appears black, in whatfoever direc- 

 tion it is viewed. 



From feveral experiments, and obfervations, 

 which I have made, in the courfe of this inquiry, 

 it appears, that the rays of light are tranfmitted 

 throughTranfparent Coloured Subftances by means 

 of a power, with which they are endued j and, 

 that thofe Media tranfmit Coloured Light with 

 the greateft ftrength, which have the greatefl 

 refraftive power. 



The ftrong refractive, and refleflive, power of 

 inflammable bodies has been obferved by Sir 

 Ifaac Newton- But, the power, of fuch bodies, 

 to tranfmit the rays otherwife than by refra<flino- 

 them, has not, I believe, hitherto been noticed. 



The following experiments prove, that the 

 TranfmifTive Power, of Inflammable Coloured 

 Media is much ftronger, than the Tranfmiflive 



K 3 Power 



