XXVII. The endeavour of the flame to ascend, is the proof which is vulgarly exhibited, of there being an element or sphere of fire above us, by those who maintain that position; but we shall shew, that this is a very feeble proof, even admitting their own state of the case, because every thing that is lighter than the fluid that surrounds it, will, if it is not by violence restrained from doing so, rise above it, without being invited to ascend by a sphere of its own species that is aloft; and it is from hence, that flame, smoke, vapour, an infinity of elemental effluvia, and divers other species of things ascend, without the assistance or intervention of any other cause, except that of their being lighter than the inferior gross air. XXVIII. To this we shall add, that there is not in the flame, the propensity to ascend which they suppose, and which seems to be indicated by its rising upwards in a conic form; for this ascent is violent, and not natural to the flame. We shall illustrate this paradox, by an experiment which my Lord Bacon mentions in the first Book of his Centuries. A small wax candle, fitted into an iron tube, and placed perpendicular in a vessel filled with spirit of wine, in which it must be immersed to such a depth, that when they are both set fire to, the flame of the candle shall not rise higher than that of the spirit; and you will see, the flame of the candle and that of the spirit being distinguishable by their different colour, that the flame of the candle will appear in the middle of that of the spirit, extending itself in breadth, and not in a pyramidical, but a round form, that occupies four or five times as much space, as that which it used to occupy when burning in the open air. This experiment proves, that the pyramidical form which the flame regularly assumes, is caused by the pressure of the air that surrounds it; and this is the sentiment of the modern philosophers, who without adverting to the experiment we have mentioned, would make no scruple of pronouncing, that the form it assumes is a violence done the flame. XXIX. By this example it may be seen, that experiments, provided they are made with judgment, and attended to with subtil reflection, are the only means by which we can attain any certain knowledge of natural things; but if they are made in a lumping way, and without due attention, and exactness, they are the occasion of innumerable errors. Many have arisen, from attributing to a native inclination, or intrinsic virtue of some body, effects, which are only caused by the impulse of some other neighbouring body. Before the gravity and elasticity of the air were discovered, it was looked upon as a thing demonstrated by experience, that the water’s rising in the pump, was from its inclination to obstruct or oppose a vacuum, and now it is a thing evinced by experience, that the air is what impels it to that ascent. PARADOX IX.