Passage (Michael Faraday, *The Chemical History of a Candle*, Lecture I, 1860–61, continued): "In this wood we have one of the most beautiful illustrations of the general nature of a candle that I can possibly give. The fuel provided, the means of bringing that fuel to the place of chemical action, the regular and gradual supply of air to that place of action — heat and light — all produced by a little piece of wood of this kind, forming, in fact, a natural candle. But we must speak of candles as they are in commerce. Here are a couple of candles commonly called dips. They are made of lengths of cotton cut off, hung up by a loop, dipped into melted tallow, taken out again and cooled, then re-dipped until there is an accumulation of tallow round the cotton." In Faraday's framework, a candle consists of which of the following essential elements?