Fourthly, I have very often taken notice of, and also observ'd with a
_Microscope_, certain excrescencies or Ebullitions in the snuff of a
Candle, which, partly from the sticking of the smoaky particles as they are
carryed upwards by the current of the rarify'd Air and flame, and partly
also from a kind of Germination or Ebullition of some actuated unctuous
parts which creep along and filter through some small string of the Week,
are formed into pretty round and uniform heads, very much resembling the
form of hooded Mushroms, which, being by any means expos'd to the fresh
Air, or that air which encompasses the flame, they are presently lick'd up
and devour'd by it, and vanish.
The reason of which _Phaenomenon_ seems to me, to be no other then this:
That when a convenient thread of the Week is so bent out by the sides of
the snuff that are about half an Inch or more, remov'd above the bottom, or
lowest part of the flame, and that this part be wholly included in the
flame; the Oyl (for the reason of filtration, which I have elsewhere
rendred) being continualy driven up the snuff is driven likewise into this
ragged bended-end, and this being remov'd a good distance, as half an Inch
or more, above the bottom of the flame, the parts of the air that passes by
it, are already, almost satiated with the dissolution of the boiling
unctuous steams that issued out below, and therefore are not onely glutted,
that is, can dissolve no more then what they are already acting upon, but
they carry up with them abundance of unctuous and sooty particles, which
meeting with that rag of the Week, that is plentifully fill'd with Oyl, and
onely spends it as fast as it evaporates, and not at all by dissolution or
burning, by means of these steamy parts of the filterated Oyl issuing out
at the sides of this ragg, and being inclos'd with an air that is already
satiated and cannot prey upon them nor burn them, the ascending sooty
particles are stay'd about it and fix'd, so as that about the end of that
ragg or filament of the snuff, whence the greatest part of the steams
issue, there is conglobated or fix'd a round and pretty uniform cap, much
resembling the head of a Mushrom, which, if it be of any great bigness, you
may observe that its underside will be bigger then that which is above the
ragg or stem of it; for the Oyl that is brought into it by filtration,
being by the bulk of the cap a little shelter'd from the heat of the flame,
does by that means issue as much out beneath from the stalk or downwards,
as it does upwards, and by reason of the great access of the adventitious
smoak from beneath, it increases most that way.
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