es them to his
Correspondent, as follows:

[Sidenote: _The Exclusion of _all_ Air is here necessary, because Air being
subject to the operation of Heat and Cold, if any of it remain in the
_Barometer_, it will cause it to vary from shewing the true Pressure of the
Air._]

1. My _Wheel-barometer_ I could never fill so exactly with _Mercury_ as to
exclude _all_ Air; and therefore I trust more {156} to a _Mercurial_ Cane,
and take all my Notes from it. This Cane is but 35. Inches long, of a very
slender Cavity, and thick Glass. This may easily be conveyed to any place,
for Trials. The Vessel for the stagnating _Mercury_, into which the said
Cane is immersed, is about two _Inches_ wide. The _Mercury_ so well fill'd,
that for some daies it would not subside, but hung to the top of the
Glass-cane. I keep it in a Closet pretty close, 9. foot high, 8. foot
broad, 15. foot long; neer a Window. This I note, because possibly the
closeness of the room may hinder, that it gives not the full of all
Changes, as it might in a more passable Air.

2. In all my Observations from _May_ 28. 1664 to this present (_December_
9. 1665.) the Quicksilver never ascended but very little above 301/4 Inches.

3. It ascended very seldom so high (_videl._ to 301/4 Inches) chiefly
_Decemb._ 13. 1664. the weather being fickle-fair, Evening.

4. I find by my _Calender_ of _June_ 22. 1664. at 5. in the Morning, in a
time of long setled fair weather, that the _Mercury_ had ascended about
half an Inch higher then 30: but I fear some mistake, because I then took
no impression of _wonder_ at it; yet for 3. or 4. daies, at that time it
continued high, in well-setled, fair and warm weather; most part above 30.
Inches. So that I may note, the _Mercury_ to rise as high in the hottest
_Summer_, as in the coldest _Winter-weather_.

[Sidenote: _Perhaps this is from some included Air._]

5. Yet surely I have noted it ascend a little higher for the Coldness of
the Weather; and very frequently, both in {157} Winter and Summer to be
higher in the cold Mornings and Evenings, then in the warmer Mid-day.

6. Generally in setled and fair weather both of Winter and Summer, the
_Mercury_ is higher, than a little _before_ or _after_, or _in_ Rainy
weather.

7. Again, generally it descended lower after Rain, than it was before Rain.

[Sidenote: _It seems these were _Easterly_ winds._]

8. Generally also it falls in great winds; and somewhat it seem'd to sink,
when I