340 Observations on the Flame of a Candle. (May, 
tallow is at the same time increased, do not seem to me to have 
ever been correctly stated. The only reason I have ever seen 
assigned for it in chemical works is, that in this situation the fused 
tallow is carried up to the top of the wick; and the volatile products 
into which it is there converted not having to pass through so great 
a length of flame as when the wick is short, are not so completely 
burned. ‘This explanation is unsatisfactory, because it does not 
show why the flame does not ascend as high as the volatile inflam- 
mable materials supposed to escape unburnt above it ; and it is in- 
correct, for the fused tallow does not rise to the top of a long wick; 
as may be proved by observing the real height to which it rises, by 
placing-the candle nearly in a horizontal position, when the fame 
will extend laterally as far towards the end of the wick as the fused 
tallow proceeds, and leave the rest of the wick unsurrounded by 
flame. Besides, I find that an equal diminution of light may be 
produced by lowering a metallic cylinder of the size of the wick 
from the apex of the flame to the summit of a short wick. In this 
instance there cannot be any fluid tallow drawn up too high; and 
some other cause tor the loss of light must, therefore, be sought 
for. 
To me it appears that there are two causes operating at the same 
time in producing the obscuration in question : the one is the opacity 
of the wick; and the other is its conducting power. In order to 
have an idea of the effect of its opacity, imagine a room illuminated 
by rows of lamps disposed round a central black pillar, and con- 
ceive what would be the increase of light in every part of the room 
by the removal of this central pillar, which, from its situation, must 
have intercepted the rays of light from nearly half the lamps in 
every direction, and from its colour could not have restored back 
any of those rays by reflection. If, instead of lamps, a sheet of 
flame surrounding the pillar be conceived, the analogy to the un- 
snuffed candle will be still stronger, and the prejudicial influence of 
the wick be better illustrated. But in order that this explanation 
should be acceded to, I must first show that the opinion that “ flame 
is an opaque body,” is erroneous ; for, were it really opaque, it would 
be of comparatively little consequence whether any solid body oc- 
cupied its centre or not.. Let, therefore, the following experiments 
be made :— 
‘Light a spirit lamp, and also a tallow candle. Then try to ob- 
serve the flame of the spirit lamp through that of the candle, and 
you will find that you cannot succeed. Now reverse the experi- 
ment ; and you will see clearly the flame of the candle through that 
of the lamp. Remove now the spirit lamp; and substitute for it 
another candle. Let both the candles burn until they require 
snuffing very much ; then snuff but one of them; and on trying to 
Jook through the upper part of the flame of the one burning bril- 
liantly at the flame of the other burning in a dull manner, you will 
find the attempt vain: but, by changing the situations of the two 
candles, you may easily see the bright flame through the dull one. 
