the Light cj bodies in a State of Combufiion, 197 



gradual manner which I have already defcribed. A piece of 

 rotten wood, whilil: burning, will exemplity and confirm the 

 preceding illuftration. When influenced by the external air 

 only, if examined through a prifm, no rays will be found to 

 efcape but the orange and the red. By blowing upon the 

 burning wood with a pair of bellows, the com bullion, 

 being; increafed, will affect thofe internal parts of the body 

 which were not adled upon before. Thefe parts, therefore, 

 will begin to lofe their light, and a prifm will {hew the 

 green, the blue, the violet, and indlgOy all appearing in fuc- 

 ceffion* Appearances hmilar to the preceding may be ob- 

 ferved in a common kitchen fire. When it is fainted:, its 

 colour is moll: red, the other rays having been emitted, and 

 the combuftion at a fland ; but by blowing upon it in this 

 ftate, its brightnefs will be increafed, and more and more of 

 the rays which are yielded by the internal parts of the body 

 will come to the eye, till at length, by continuing to blow, the 

 combufiion will be made fo complete as to yield all the rays, 

 or to make it appear perfectly white. 



Many are the varieties difcoverable in the flanies and In the 

 appearances of fixed burning bodies to which the preceding 

 obfervations may be applied ; but, to avoid unnecefl'ary amplifi- 

 cation I will take notice only of what appears to me an imper- 

 fedion in Sir Isaac Newton's definition of flams. He con- 

 je6i:ures, that it may be a vapour heated red-hot. I think I 

 fliould rather fliy, that flame Is an inflance of combufiion 

 whofe colour will be determined by the degree of decon.ipofi- 

 tloii which takes place. If it be very imperfe^l, the molf 

 refrangible rays only will appear. If it be very perfe<5l, all 

 the rays will appear, and its flame will be brilliant in 



proportiof\ 



