Equilibr turn j you may, I fay, determine, What known 
weight in the Statical Barofcope anfwers fuch determinate Al* 
titudes of the a'fcending and defcending Quiek-filver in the 
Mercurial. And if the Ballance be accommodated with a di- 
vided Arch, or a Wheel and Index, thefe Obfervations will 
affift yon for the future to determine readily ? by feeing the 
inclination of the Cock or the degree mark’d by thelndex,wha£ 
pollency the Buble hath, by the change of the Atmoffheres 
weight, acquired or loft. Some Obfervations of this nature 
I watchfully made, fometimes putting in a ^4 th » fometimes a 
fometimes aitf th ; and fometimes heavier parts of a Grain, 
to the lighter Scale. But one, that knew not, for what ufes thole 
little papers were, coming to a window, where my Barofcopes 
flood , fo unluckilyihook them out of the Scales, and con- 
founded them, that he robb’d me of the opportunity of ma- 
king the nice Obfervations I intended , though I had the fatif- 
{ adtion of feeing, that they were to be made. 7. By this Sta « 
tical Inftrument we may be affifted to compare the Mercurial 
Barofcopes of fcveral places (though never fo diftantj and to 
make fome Eftimates of the Gravities of the Air therein. As 
if, for ihftance, I have found by Obfervation, that the Buble, I 
employ, (and one may have divers Bubles of feveral fizes, that 
the one may repaire any mifchance, that may happen to ano- 
ther) weigh’d juft a Drachme , when the Mercurial Cylinder 
was at the height of 29 j inches (which in fome places I have 
found a mcderate\ altitudes) and that the Addition of the 1 6th 
part of a gr. is requifite to keep the Buble in an Equilibrium, 
when the Mercury is rifen an 8th, or any determinate part of an 
inch above the former ftation : When I come to another place, 
where there is a Mercurial Barometer, as well freed from Air 
as mine ( for that muft be fuppofed ) if taking out my Scale in- 
ftrumenr, it appeare to weigh precifely a Drachme, and the 
Mercury in theBarofcope there ftand at juft 29! inches, we may 
conclude the Gravity of the Atmofphere not to be fenfibly un- 
equal in both thofe two places, though very diftant. And 
though there be no Barofcope there, yet if there be an additi- 
onal weight, as for inftance, the idth part of a Grain requifite 
to be added to the Buble, to bring the fcales to an Equilibrium, 
ii will appear that the Air at this fecond place is, at that time 
fo 
