246 Mr. Delaval on the Caufe of the 



Power of Coloured Media, which do not abound 

 in phlogiftic matter. 



To a dilute folution of green vitriol in diftilled 

 water, 1 added a fmall quantity of an aqueous in- 

 fufion of galls. The liquor, compofcd of thefe 

 ingredients, tranfnnitted a blue colour, which, al- 

 though perfe6lly diftinfl, and unmixed with any 

 other hue, was not vivid, but appeared as a co- 

 loured fubftance not a6ling upon a fufficient 

 quantity of the rays of its own colour. 



I made a tindlure, by digefling green vitriol 

 in fpirit of wine, and, to a portion of this tindlure, 

 diluted with a farther addition of fpirit of wine, 

 I applied a fmall quantity of a ftrong fpirituous 

 tin6luie of galls. This liquor, thus prepared, 

 tranfmitted a blue colour, greatly excelling in 

 beauty and brightnefs. 



The ftrength, of the tranfmiflive power of in- 

 flammable media, is manifeft from a comparative 

 view of thefe procefles, and others which have 

 been already inftanced. 



Sir Ifaac Newton attributed the colours of 

 natural bodies, to the feveral fizes and denfities 

 of their particles, by which, according to him, 

 they refleB feveral forts of rays, and thereby 

 appear of feveral colours. 



It has been fhewn, throughout this inquiry, that 

 the Colouring Particles are not endued with a 

 refieftive power, but produce their feveral colours 

 by tranfmitting the feveral forts of rays. 



The 



