ip 2 Mr. Morgan’s OlfervaiioMf and Experiments on 
By examining the flame of a common caudle we may ob* 
ferve, that its lowed extremities, or the part in which the black 
colour of the wick terminates, di (charges the lead heat ; and 
that, as the vertex of the flame is approached, a fucceffive order 
of parts is paffed through, in which the lowed is continually 
adding to the heat of what is jud above it, till we come to 
the top of the flame, near which all the heat is colleded into a 
focus. At the lowed extremity, however, where the heat is 
inconfiderable, a blue colour may be always obferved ; and 
from this appearance, amongd others, it may, I think, be 
fafely concluded, that the blue rays are fome of thofe which 
efcape from combudibles in an early period of their decompo- 
fition ; and that if the decomposition could be examined in a 
■period dill 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 
mod beautifully coloured with the violet and indigo rays. To 
the preceding indance of a common candle many fadts may 
be added, which fpeak a flmilar language. If fulphur or 
sether is burned, or any of thofe combudibles 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 confid of the violet, the indigo, the blue, and fometimes a 
fmall quantity of the green rays. The bed mode, however, 
of (hewing the efcape of fome rays oy that degree of heat 
which will not feparate others till increafed, is the following. 
Give a piece of brown paper a fpherical form, by preffing it 
upon 
