One of the most imaginative (and spectacular) experiments of Sylva Sylvarum is the experiment describing how to create (in laboratory) a flame-within-a-flame. It is both ingenious in its construction and bold in its interpretation – because Bacon claims that this experiment is modelling, artificially, the conditions in heavens. The flame of a candle burning inside of a vessel with alcohol (spirit of vine) is nothing less than a model of a star.
See here for an annotated translation of it.
31. Take a small wax candle, and put it in a socket of brass or iron; then set it upright in a porringer full of spirit of wine heated; then set both the candle and spirit of wine on fire, and you shall see the flame of the candle open itself, and become four of five times bigger than otherwise it would have been; and appear in figure globular, and not in pyramis. You shall see also, that the inward flame of the candle keepeth colour, and doth not wax any whit blue towards the colour of the outward flame of the spirit of wine. This is a noble instance; wherein two things are most remarkable: the one, that one flame within another quentcheth not; but is a fixed body, and continueth as air or water do. And therefore flame would still ascend upwards in one greatness, if it were not quenched on the sides: and the greater the flame is at the bottom, the higher is the rise. The other, that flame doth not mingle with flame, as air doth with air, or water with water, but only remained contiguous. as it cometh to pass betwixt consisting bodies. It appeareth also that the form of a pyramis in flame, which we usually see, is merely an accident, and that the air about, by quenching the sides of the flame, crusheth it, and extenuateth it into that form; for of itself it would be round; and therefore smoke is in the figure of a pyramis reversed; for the air quencheth the flame and receiveth the smoke. Note also that the flame of the candle, within the flame of the spirit of wine, is troubled; and doth not only open and move upwards, but moveth waving, and to and fro; as if flame of his own nature (if it were not quenched) would roll and turn, as well as move upwards. By all which it should seem that the celestial bodies (most of them) are true fire or flames, as the Stoics held; more fine (perhaps) and rarified than our flame is. For they are all globular and determinate; and they have rotation; and they have the colour and splendor of flame; so that flame above is durable, and consistent, and in his natural place; but with us it is a stranger, and momentany, and impure; like Vulcan that halted with his fall.