ly from Light than
those of other Colours do, by reason that the Light falling on them is
not reflected outwards, but enters the Bodies, and is often reflected
and refracted within them, until it be stifled and lost?

_Qu._ 7. Is not the strength and vigor of the action between Light and
sulphureous Bodies observed above, one reason why sulphureous Bodies
take fire more readily, and burn more vehemently than other Bodies do?

_Qu._ 8. Do not all fix'd Bodies, when heated beyond a certain degree,
emit Light and shine; and is not this Emission perform'd by the
vibrating motions of their parts? And do not all Bodies which abound
with terrestrial parts, and especially with sulphureous ones, emit Light
as often as those parts are sufficiently agitated; whether that
agitation be made by Heat, or by Friction, or Percussion, or
Putrefaction, or by any vital Motion, or any other Cause? As for
instance; Sea-Water in a raging Storm; Quick-silver agitated in _vacuo_;
the Back of a Cat, or Neck of a Horse, obliquely struck or rubbed in a
dark place; Wood, Flesh and Fish while they putrefy; Vapours arising
from putrefy'd Waters, usually call'd _Ignes Fatui_; Stacks of moist Hay
or Corn growing hot by fermentation; Glow-worms and the Eyes of some
Animals by vital Motions; the vulgar _Phosphorus_ agitated by the
attrition of any Body, or by the acid Particles of the Air; Amber and
some Diamonds by striking, pressing or rubbing them; Scrapings of Steel
struck off with a Flint; Iron hammer'd very nimbly till it become so hot
as to kindle Sulphur thrown upon it; the Axletrees of Chariots taking
fire by the rapid rotation of the Wheels; and some Liquors mix'd with
one another whose Particles come together with an Impetus, as Oil of
Vitriol distilled from its weight of Nitre, and then mix'd with twice
its weight of Oil of Anniseeds. So also a Globe of Glass about 8 or 10
Inches in diameter, being put into a Frame where it may be swiftly
turn'd round its Axis, will in turning shine where it rubs against the
palm of ones Hand apply'd to it: And if at the same time a piece of
white Paper or white Cloth, or the end of ones Finger be held at the
distance of about a quarter of an Inch or half an Inch from that part of
the Glass where it is most in motion, the electrick Vapour which is
excited by the friction of the Glass against the Hand, will by dashing
against the white Paper, Cloth or Finger, be put into such an agitation
as to emit Light, an