as well in Winter, and several times in Summer (for I was often absent during that season) as the Spring, yet the frequency of their Vicissitudes (which perhaps was but accidental) made them more pleasant in the latter of these seasons. So that, the matter of Fact having been made out by variety of repeated Observations, and by sometimes comparing severall of those new _Baroscopes_ together, I shall add some of those Notes about this Instrument, which readily occur to my memory, reserving the rest till another opportunity. And _First_, if the ground, on which I went in framing this _Baroscope_, be demanded, the answer in short may be; 1. That, though the Glass-buble, and the Glass-counterpoise, at the time of their first being weigh'd, be in the Air, wherein they both are weigh'd, exactly of the same weight; yet they are nothing near of the same bulk; the Buble, by reason of its capacious cavity (which contains nothing but Air, or something that weighs less than Air) being perhaps a hundred or two hundred times (for I have not conveniency to measure them) bigger than the Metalline counterpoise. 2. That according to a _Hydrostatical_ Law (which you know I have lately had occasion to make out) If two Bodies of equal gravity, but unequal bulk come to be weigh'd in another _Medium_, they will be no longer {234} equiponderant; but if the new _Medium_ be heavier, the greater Body, as being lighter in _Specie_, will loose more of its weight, than the lesser and more compact; but if the new _Medium_ be lighter than the first, then the bigger Body will outweigh the lesser; And this disparity, arising from the change of _Medium's_, will be so much the greater, by how much the greater inequality of bulk there is between the Bodies formerly equiponderant. 3. That, laying these two together, I consider'd, that 'twould be all one, as to the effect to be produced, whether the Bodies were weighed in _Mediums_ of differing gravity, or in the same _Medium_, in case its (_specifick_) gravity were considerably alter'd: And consequently, that since it appear'd by the _Baroscope_, that the weight of the Air was sometimes heavier, and sometimes lighter, the alterations of it, in point of gravity, from the weight, it was off at first counterpoising of the Buble of it, would _unequally_ affect so large and hollow a Body, as the Buble, and so small and dense a one, as a Metallin weight: And when the Air by an increase of gravity should become a heavier _Medium_, than before, it would buoy up the Glass more than the Counterpoise; and if it grew lighter, than it was at first, would suffer the former to preponderate: (The Illustrations and Proof can scarce be added in few words; but, if it be desired, I may, God permitting, send you them at my next leasure:) And though our English Air be about a thousand times lighter, than water, the difference in weight of so little Air, as is but equal in bulk to a Buble,