and Servant.
[XLI.]
MADAM,
My answer to your Authors question, Why flame ascends in a pointed figure?[1] is, That the figure of fire consists in points, and being dilated into a flame, it ascends in lines of points slope-wayes from the fired fuel; like as if you should make two or more sticks stand upright and put the upper ends close together, but let the lower ends be asunder, in which posture they will support each other, which, if both their ends were close together, they could not do. The second question is, Why fire doth not alwayes flame?[2] I answer, Because all fuel is not flameable, some being so moist, as it doth oppose the fires dryness, and some so hard and retentive, as fire cannot so soon dissolve it; and in this contest, where one dissipates, and the other retains, a third figure is produced, viz. smoak, between the heat of one, and the moisture of the other; and this smoak is forced by the fire out of the fuel, and is nothing else but certain parts of fuel, raised to such a degree of rarefaction; and if fire come near, it forces the smoak into flame, the smoak changing it self by its figurative motions into flame; but when smoak is above the flame, the flame cannot force the smoak to fire or enkindle it self, for the flame cannot so well encounter it; which shews, as if smoak had a swifter motion then flame, although flame is more rarified then smoak; and if moisture predominate, there is onely smoak, if fire, then there is flame: But there are many figures, that do not flame, until they are quite dissolved, as Leather, and many other things. Neither can fire work upon all bodies alike, but according to their several natures, like as men cannot encounter several sorts of creatures after one and the same manner; for not any part in nature hath an absolute power, although it hath self-motion; and this is the reason, that wax by fire is melted, and clay hardened. The third question is, Why some few drops of water sprinkled upon fire, do encrease its flame? I answer, by reason of their little quantity, which being over-powred by the greater quantity and force of fire, is by its self-motions converted into fire; for water being of a rare nature, and fire, for the most part, of a rarifying quality, it cannot suddenly convert it self into a more solid body then its nature is, but following its nature by force it turns into flame. The fourth question is, Why the flame of spirit of Wine doth consume the Wine, and yet cannot burn or hurt a linnen cloth? I answer, The Wine is the fuel that feeds the flame, and upon what it feeds, it devoureth, and with the food, the feeder; but by reason Wine is a rarer body then Oyle, or Wood, or any other fuel, its flame is also weaker. And thus much of these questions, I rest,
Madam,
Your Faithful Friend
and Servant.
[1] P. 4. art. 97.
[2] Art. 107.