Page:Philosophical Transactions - Volume 001.djvu/249

 exquisit Æquilibrium; you may, I say, determine, What known weight in the Statical Baroscope answers such determinate Altitudes of the ascending and descending Quick-silver in the Mercurial. And if the Ballance be accommodated with a divided Arch, or a Wheel and Index, these Observations will assist you for the future to determine readily, by seeing the inclination of the Cock or the degree mark'd by the Index, what pollency the Buble hath, by the change of the Atmospheres weight, acquired or lost. Some Observations of this nature I watchfully made, sometimes putting in a 64th sometimes a 32th sometimes a 16th and sometimes heavier parts of a Grain, to the lighter Scale. But one, that knew not, for what uses those little papers were, coming to a window, where my Baroscopes stood, so unluckily shook them out of the Scales, and confounded them, that he robb'd me of the opportunity of making the nice Observations I intended, though I had the satisfaction of seeing, that they were to be made. 7. By this Statical Instrument we may be assisted to compare the Mercurial Baroscopes of several places (though never so distant) and to make some Estimates of the Gravities of the Air therein. As if, for instance, I have found by Observation, that the Buble, I employ, (and one may have divers Bubles of several sizes, that the one may repaire any mischance, that may happen to another) weigh'd just a Drachme, when the Mercurial Cylinder was at the height of 29 inches (which in some places I have found a moderate altitude;) and that the Addition of the 16th part of a gr. is requisite to keep the Buble in an Æquilibirum, when the Mercury is risen an 8th, or any determinate part of an inch above the former station: When I come to another place, where there is a Mercurial Barometer, as well freed from Air as mine (for that must be supposed) if taking out my Scale instrument, it appeare to weigh precisely a Drachme, and the Mercury in the Baroscope there stand at just 29 inches, we may conclude the Gravity of the Atmosphere not to be sensibly unequal in both those two places, though very distant. And though there be no Baroscope there, yet if there be an additional weight, as for instance, the 16th part of a Grain requisite to be added to the Buble, to bring the scales to an Æquilibrium, it will appear that the Air at this second place is, at that time Rh