the Light of Bodies in a State of Combujlion, j 9 ; 



2. The blue colour of a fulphurcous flame in pure air is 

 •changed into a dazzling white. 



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

 trous air, is green. It is white flrongly tinged wjth the indigo 

 and violet when mixed with common air ; but when mixed 

 with dephlogifticated air, or furrounded by it, the brilliancy 

 of its flame is moft Angularly beautiful. 



If the preceding fa^ls prove that light, as an heterogeneous 

 body, is gradually decompofed during combuftion ; if they 

 prove, likewife, that the indigo rays efcape with the leaf!: hear, 

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

 count for feveral Angularities in the colours of different flames. 

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

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

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

 dently in that weak flate of decompofition, in which the mofl 

 refrangible rays efcape in the greatefl abundance ; but of thefe 

 rays the green efcape moil 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 greatefl perfection 

 in brafs founderies. The heat in this inflance, 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 objeds around a very pallid or 

 ghaflily appearance, which is the confequence of its wanting 

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

 white* 



C c a The 



