i(^z My. Morgan's Ohfa'vallons and Expdr'unents on 



By examining the flame of a common candle we may ob- 

 fervc, that its iowefl extremities, or the part in which the black 

 colour of the wick terminates, dilcharges the lead heat; and 

 that, as the vertex of the flame is approached, a fucceffive order 

 ot parts is paflld through, in whicii the loweft is continually 

 adding to the heat of what is juft above it, till w^e come to 

 the top of the flame, near which all the heat is collecled into a 

 focus. i\t the loweil extremity, however, where the heat is 

 inconfiderable, a blue colour may be always obferved ; and 

 from this appearance, amongfi others, it may, I think, be 

 fafely concluded, that the blue rays are fome of thofe which 

 efcape from combuflibles in an early period of their decompo- 

 fition ; and that if the decompofition could be examined in a 

 period flill more early, the colour of their flame would be 

 violet. By an a priori deduction of this kind, I was led to 

 watch the appearances of a candle more attentively ; whence I 

 found that to the external boundary of a common candle 

 is annexed a filament of light, which, if proper care be 

 taken to prevent the efcape of too much fmoke, will appear 

 moft beautifully coloured with the violet and indigo rays. To 

 the preceding inftance of a common candle many fa£ls may 

 be added, which fpeak a fimilar language. If fulphur or 

 asther is burned, or any of thofe combuflibles whofe 

 vapour is kindled in a fmall degree of heat, a blue flame 

 will appear, which, if examined by the prifm, will be found 

 to confrft of the violet, the indigo, the blue, and fometimes a 

 fmall quantity of the green rays. The beft mode, however, 

 of (hewing the efcape of fome rays by that degree of heat 

 which will not feparate others till increafed, is the following. 

 Give a piece of brown paper a fpherical form, by prefling it 



upon 



