the Light of Bodies in a State of Combufion. \ ^ ;; 



2. The blue colour of a fulphureous flame ia pure air is 

 •changed into a dazzling white. 



a. The flame of inflammable air, when mixed with ni- 

 trous air, is green. It is white flrongly tinged w^iththe indigo 

 and violet when mixed with common air; but when mixed 

 with dephlogifticated air, or furrounded by it, the brilliancy 

 rof its flame is moll Angularly beautiful. 



If the preceding fa6ts prove that light, as an heterogeneous 

 body, is gradually decompofed during combuftion ; if they 

 prove, likewife, that the indigo rays efcape with the leafl: heat^ 

 and the red with the greateil: ; I think we may rationally ac- 

 count for feveral iingularities in the colours of different flames. 

 If a piece of paper, impregnated with a folution of copper in 

 the nitrous acid, be let on fire, the bottom and fides of the 

 flame are always tinged with green. Now this flame is evi- 

 dently in that weak ftate of decompofition, in which the mofi 

 refrangible rays efcape in the greateft abundance; but of thefe 

 rays the green efcape mofl: plentifully through the unignited 

 vapour and that portion of the atmofphere which feparates the 

 eye from the flame. The peculiarity which I have now endea- 

 voured to account for may be obferved in the greateft perfedion 

 in brafs founderies. The heat in this inftance, though very 

 ftrong, is fcarcely adequate to the decompofition of the metallic 

 vapour which efcapes from the melted brafs. A very Angular 

 flame therefore appears to the eye ; for while its edges are green, 

 its body is fuch as to give the objects around a very pallid or 

 ghaftly appearance, which is the confequence of its wanting 

 that portion of red rays which is neceflTary to make a perfed 

 white. 



C c a The 



