Having thus in _General_ expressed his thoughts about this Invention, and the singular pleasure, he takes in the Observations made therewith, he descends to particulars, and in several Letters communicates 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 open'd a wide door to it, to let in stormy winds; yet I have found it to continue very high, in a long stormy wind of 3. or 4. daies. 9. Again, generally it is higher in an _East_ and _North_-wind. (_Caeteris paribus_) than in a _South_ and _West_-wind.