bserv'd to be an Earthquake;
yet I remember about that time (whether precisely then or not; I cannot
say) I took notice of some kind of odde shaking or heaving I observed in my
study, but did impute it to the going of Carts or Coaches, supposed to be
not far off; though yet I did take notice of it, as a little differing from
what is usual on such occasions; (and wondered the more, that I did not
hear any:) But not knowing, what else to refer it to, I thought no more of
it. And the like account I have had from some others in _Oxford_, who yet
did not think of an Earth-quake; it being a rare thing with us. Hearing
afterwards of an Earthquake observed by others; I looked on my Notes
concerning my _Thermoscope_ and _Baroscope_, to see if any alteration
considerable had then happened.

My _Thermoscope_ consists of a round large Glass, containing about half a
pint or more; from whence issues a long Cylindrical neck of Glass, about
two foot and a half in length, and less than a quarter of an inch diameter;
which neck was _hermetically_ sealed at the top, to exclude communication
with the External Air; but before the sealing of it, the whole Glass was
filled with _Spirit of Wine_ (tinged with _Cochineel_, to make it the more
discernable to the Eye) so warmed, that it filled the whole content of the
Glass; but afterwards, as it cooled, did so subside, as to leave a void
space in the upper part of the Neck. Which Instrument, so prepared, doth by
the rising or falling of the tinged liquor in the neck (consequent upon the
expanding or contracting of the whole liquor contained in it and the Ball
below) give a very nice account of the Temperature of the Air, {167} as to
_Heat_ or _Cold_: Even so nice, as that my being or not being in my Study I
find to vary its hight sometimes almost a quarter of an inch.

My _Baroscope_, I call another Instrument for estimating the _Weight_ or
_Pressure_ of the Incumbent Air, consisting of a long _Glass-tube_ of about
4. foot in length, and about a quarter of an inch Bore: which tube
(_hermetically_ sealed at the one end) being filled with Quicksilver
(according to the _Torricellian_ Experiment) is inverted, so as to have the
open end of it immersed in Stagnant Quicksilver, contained in a larger
Glass under it, exposed to the pressure of the outward Air: Out of which
open end (after such immersion) the Quicksilver in the Tube being suffered
to run out, as much as it will, into the Stagnant Quicksilve