with a red, may be presently ting'd with a yellow, blew, green, purple, or
the like, by altering the appropinquation of the terminating Plates. Now
that air is not necessary to be the interposed body, but that any other
transparent fluid will do much the same, may be tryed by wetting those
approximated Surfaces with Water, or any other transparent Liquor, and
proceeding with it in the same manner as you did with the Air; and you will
find much the like effect, only with this difference, that those comprest
bodies, which differ most, in their refractive quality, from the
compressing bodies, exhibit the most strong and vivid tinctures. Nor is it
necessary, that this _laminated_ and _ting'd_ body should be of a fluid
substance, any other substance, provided it be thin enough and transparent,
doing the same thing: this the _Laminæ_ of our _Muscovy-glass_ hint; but it
may be confirm'd by multitudes of other Instances.

And first, we shall find, that even Glass it self may, by the help of a
Lamp, be blown thin enough to produce these _Phænomena_ of Colours: which
_Phænomena_ accidentally happening, as I have been attempting to frame
small Glasses with a Lamp, did not a little surprize me at first, having
never heard or seen any thing of it before; though afterwards comparing it
with the _Phænomena_, I had often observed in those Bubbles which Children
use to make with Soap-water, I did the less wonder; especially when upon
Experiment I found, I was able to produce the same _Phænomena_ in thin
Bubbles made with any other transparent Substance. Thus have I produced
them with Bubbles of _Pitch_, _Rosin_, _Colophony_, _Turpentine_,
_Solutions_ of several _Gums_, as _Gum-Arabick_ in water; any _glutinous_
Liquor, as _Wort_, _Wine_, _Spirit of Wine_, _Oyl of Turpentine_, _Glare of
Snails,_ &c.

It would be needless to enumerate the several Instances, these being enough
to shew the generality or universality of this propriety. Only I must not