"The fire had not then burnt unusually low, nor was the snuff of the candle very long; the candle, however, had been blown out."

I never heard the charred part of the candle wick called the "snuff" before.

snuff
adj : snuff colored; grayish to yellowish brown [syn: snuff-brown,
mummy-brown, chukker-brown]
n 1: finely powdered tobacco for sniffing up the nose
2: a charred candlewick
3: sensing an odor by inhaling through the nose [syn: sniff]
v : sniff or smell inquiringly [syn: snuffle]


Source: Webster's Revised Unabridged Dictionary (1913)

Snuff \Snuff\, v. t. [imp. & p. p. Snuffed; p. pr. & vb. n.
Snuffing.] [OE. snuffen. See Snuff of a candle Snuff to
sniff.]
To crop the snuff of, as a candle; to take off the end of the
snuff of.

To snuff out, to extinguish by snuffing.
Snuff \Snuff\, v. t.[Akin to D. snuffen, G. schnupfen,
schnuppen, to snuff, schnupfen a cold in the head, schnuppen
to snuff (air), also, to snuff (a candle). Cf. Sniff,
Snout, Snub, v. i.]
1. To draw in, or to inhale, forcibly through the nose; to
sniff.

He snuffs the wind, his heels the sand excite.
--Dryden.

2. To perceive by the nose; to scent; to smell.
Snuff \Snuff\, n. [Cf. G. schnuppe candle snuff, schnuppen to
snuff a candle (see Snuff, v. t., to snuff a candle), or
cf. Snub, v. t.]
The part of a candle wick charred by the flame, whether
burning or not.

If the burning snuff happens to get out of the
snuffers, you have a chance that it may fall into a
dish of soup. --Swift.