10. I tryed several times, by strong fumes and thick smoaks to alter the Air in my Closet; but I cannot affirm, that the _Mercury_ yielded any more, then might be expected from some increase of heat. Such as have exact _Wheel-Barometers_, may try whether Odors or Fumes do alleviate the Air. 11. In this Closet I have not in all this time found the extreamest changes of the Quicksilver to amount to more, than to 23/4, or to 2-7/8. inches, at most. 12. Very often I have found great changes in the Air, without any perceptible change in the _Barometer_; as in the dewy nights, when the moisture descends in a great quantity, and the thickness sometimes seems to hide the Stars from us: In the days foregoing, and following, the Vapors have been {158} drawn up so _Invisibly_, that the Air and Sky seem'd very clear all day long. This I account a great change between ascending and descending Dews and Vapors (which import Levity and Weight,) and between thick Air and clear Air: which changes do sometimes continue in the Alternative course of day and night, for a week or fortnight together; and yet the _Baroscope_ holding the same. 13. Sometimes (I say not often) the _Baroscope_ yields not to other very great changes of the Air. As lately (_December_ 18.) an extraordinary bright and clear day; and the next following quite darkened, some Rain and Snow falling; but the _Mercury_ the same: so in high winds and calms the same. 14. I do conceive, that such as converse much _Sub dio_, and walk much abroad, may find many particulars much more exactly, then I, who have no leisure for it, can undertake. To instance in one of many, _December_ 16. last, was a clear cold day, very sharp and strong _East_ wind, the _Mercury_ very near 30. inches high, about three in the afternoon, I saw a large black cloud, drawing near us from the _East_ and _South-East_, with the _East-wind_. The _Mercury_ changed not that day nor the day following; the Stars and most of the sky were very bright and clear till Nine of the Clock; and then suddenly all the sky was darkned, yet no change of weather happened; _December_ 17. the frost held, and 'twas a clear day, till about two of the clock in the afternoon; and then many thick clouds appear'd low in the _West_; yet no change of the weather here; the Wind, Frost, and Quick-silver, the same, _December_ 18. the _Mercury_ fell almost 1/4 of an inch, and the sky and Air so clear and bright and cold with an _East-wind_, that I wondred what could cause the _Mercury_ to descend. I Expected, it should have ascended, as usually it does in such clear skys. Casually I sent my servant abroad, and he discovered the remote Hills, about 20. miles off, cover'd with {159} snow, This seem'd to manifest, that the Air, being discharged of the clouds by snow, became lighter.