seems to be of another kind. I only say, that whatever it be, it's
difficult to conceive how the Rays of Light, unless they be Bodies, can
have a permanent Virtue in two of their Sides which is not in their
other Sides, and this without any regard to their Position to the Space
or Medium through which they pass.
What I mean in this Question by a _Vacuum_, and by the Attractions of
the Rays of Light towards Glass or Crystal, may be understood by what
was said in the 18th, 19th, and 20th Questions.
_Quest._ 30. Are not gross Bodies and Light convertible into one
another, and may not Bodies receive much of their Activity from the
Particles of Light which enter their Composition? For all fix'd Bodies
being heated emit Light so long as they continue sufficiently hot, and
Light mutually stops in Bodies as often as its Rays strike upon their
Parts, as we shew'd above. I know no Body less apt to shine than Water;
and yet Water by frequent Distillations changes into fix'd Earth, as Mr.
_Boyle_ has try'd; and then this Earth being enabled to endure a
sufficient Heat, shines by Heat like other Bodies.
The changing of Bodies into Light, and Light into Bodies, is very
conformable to the Course of Nature, which seems delighted with
Transmutations. Water, which is a very fluid tasteless Salt, she changes
by Heat into Vapour, which is a sort of Air, and by Cold into Ice, which
is a hard, pellucid, brittle, fusible Stone; and this Stone returns into
Water by Heat, and Vapour returns into Water by Cold. Earth by Heat
becomes Fire, and by Cold returns into Earth. Dense Bodies by
Fermentation rarify into several sorts of Air, and this Air by
Fermentation, and sometimes without it, returns into dense Bodies.
Mercury appears sometimes in the form of a fluid Metal, sometimes in the
form of a hard brittle Metal, sometimes in the form of a corrosive
pellucid Salt call'd Sublimate, sometimes in the form of a tasteless,
pellucid, volatile white Earth, call'd _Mercurius Dulcis_; or in that of
a red opake volatile Earth, call'd Cinnaber; or in that of a red or
white Precipitate, or in that of a fluid Salt; and in Distillation it
turns into Vapour, and being agitated _in Vacuo_, it shines like Fire.
And after all these Changes it returns again into its first form of
Mercury. Eggs grow from insensible Magnitudes, and change into Animals;
Tadpoles into Frogs; and Worms into Flies. All Birds, Beasts and Fishes,
Insects, Trees, and other Vegetables, with their several Parts, grow out
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