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 Quicksilver, in which that mouth or open end is immersed, there is wont to remain (as is commonly known to those acquainted with this Experiment) a Cylinder of Quicksilver suspended in the Tube, about 28, 29, or 30. inches high; measuring from the surface of the Stagnant Quicksilver perpendicularly; (but more or less, within such limits, according as the Weight or Pressure of the Air incumbent on the External Stagnant Quicksilver exposed to it, is greater or less:) leaving the upper part of the Tube void. (Both which Instruments being the contrivance of the Honourable _Robert Boyle_, they are by him more particularly described in his _Physico-Mechanical Experiments touching the Air, Exper._ 17. and 18. and in his _Thermometrical Discourses_, premised to his _History of Cold_.) Now, according to both these Instruments, having kept a daily _Register_ of Observations for more than a whole year (saving when I have been for some short time absent from home) I find my Notes for that day to be these. _January._ |_Thermoscope._|_Baroscope._ 1665/6. Day. Hour. | inches. | inches. 19. 8. Morn. | 14-1/16. | 29-1/2. Hard frost. Close. 4. Even. | 14-3/8. | 29-1/4. Hard frost. Cloudy. 9. Even. | 14-3/4. | 29-3/4. Rain. Wind 20. 8. Morn. | 15-1/4. | 28-3/4. Sunshine. Wind.