1817.] Observations on the Flame of a Candle. 339 
The above experiment shows that it is the nearly invisible part of 
the flame which produces the most heat, and in which alone the 
atmospheric oxygen has any effect on the wire-gauze, and makes it 
probable that it is the high temperature of this part of the flame 
which occasions the decomposition of the inflammable vapour and 
gas in contact with its interior surface, thus producing and ignitirg 
the charcoal. Jt also shows that the principal deposition of the 
charcoal is not in the interior parts of the flame farthest removed 
from the air, but principally at the luminous surface, continuing 
but a very little way within it. The horizontal section by wire- 
gauze of the flame of a candle screened from currents of air proves 
the same thing. The charcoal deposited on the wires in this situa- 
tion is arranged in the form of a ring, and not in that of a black 
spot, as it has hitherto been described. Further proofs may be ob- 
tained, first, by observing that it is only on the summit of a long 
unsnuffed wick, where its edges come into contact with the Jumi- 
nous surface, and not round the body of the wick, that any deposi- 
tion of charcoal takes place: and, 2dly, by performing the follow- 
ing experiment: take a glass tube of about two inches long, open 
at both ends; its external diameter must be less than that of the 
flame of a candle, and its internal diameter about equal to that of 
the wick of the same candle; over this wick, previously snuffed, it 
must be supported in a perpendicular position while the candle is 
burning; it thus forms a kind of chimney, through which the 
vapours and gases issuing from the wick partly rise, and which may 
be set on fire at its upper extremity; when the tube has been for a 
few seconds in this position, if it be examined, it will be found to 
be coated with charcoal on its exterior surface, while its inner sur- 
face is nearly free from that substance. By conducting the un- 
burned vapour and gases off from the candle in a lateral direction, 
which may be effected by bending the above-mentioned tube once 
ata right angle, and having the horizontal portion considerably 
lengthened, much of the inflammable vapour will condense within 
the tube, fromm whence it may be collected and examined. Some 
that I collected in this manner from the burning wick of a tallow 
candle had the following properties: its colour was orange-brown ; 
smell, powerful and disagreeable, exactly the same as from a candle 
just blown out. That which condensed in the hottest part of the 
tube had the consistence of bees’-wax, and its melting point was 
about 212°; but that which condensed in the coolest part was much 
softer, and melted at 90°. When heated considerably, it takes the 
form of a white vapour; it burns with a white flame; it is insoluble 
in spirits of wine, but is very soluble in oil of turpentine ; it dis- 
solves also in liquid ammonia, and in liquid potash. Nitric acid 
has but little action on it, even when heated. From this slight 
examination, it appears to be tallow slightly altered, and rendered 
empyreumatic, but retaining most of its characteristic properties. 
The causes why the light proceeding from a candle is so much 
diminished by a long unsnuffed wick, while the consumption of the 
y 2 
