c^qmRt ^qmlibrium 5 you may, I fay, determine, Wkat known 
weight in the Statical Barofcope anfwers fuch determinate AU 
titudes of the afcending and defcending Quick-filver in the 
Mercurial. And if the Ballance be accommodated with a di- 
vided Arch, or a Wheel and Index, thefc Obfervations will 
aflift you for the future to determine readily, by feeing the 
inclination of the Cock or the degree mark'd by thelndex,whac 
pollcncy the Bnble hath, by the change of the Atmofpheres 
weight, acquired or loft. Some Obfervations of this nature 
I watchfully made, fometimes putting in a 6^^^^- fometimes a 
32'^ fometimes ^16^^^ and fometimes heavier parts of a Grain, 
ro the lighter Scale. But one, that knew not, for what ufes thofe 
little papers werCj coming to a window, where my Barofcopes 
ftood, fo unluckily fliook 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- 
fadiion of feeing, that they were to be made. 7. By this Sta- 
tical Inftrument we may be affifted to compare the Mercurial 
Barofcopes of fever al places (though never fo diftant J and to 
make fome Eftimates of the Gravities of the Air therein. As 
if, for inflance, I have found by Obfervation, that the Buble, I 
employ, (and one may have divers Bubles of feveral fizcs, that 
the one may repaire any mifchance ^ that may happen to ano- 
ther) vveigh'd juft a Drachme , when the Mercurial Cylinder 
was at the height of 29^ inches (which in fome places I have 
found a moderate\^x.\xx]^diS.O 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 Barometerj as well freed from Air 
as mine ( for that muft be fuppofed ) if taking out my Scale in- 
ftrument, it appeare to weigh precifely a Drachme, and the 
Mercury m 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 Barofcopc there, yet if there be anaddiri- 
onal weight, as for inftance, the i<^th part of a Grain requifite 
to be added Co the Buble, to bring the fcales to an JEquilmium, 
it wi.l. appear that the Air at thisfccond place is^ atthattime 
fo 
