
and without Calculation (hew the quantity of the Angle, by 
which, when the fcales propcnd either way, the Cock declines 
from the Perpendicular, and the beam from its Horizontal! pa- 
rallelifm. 
Secondly y Thofe, that will be fo curious, may, inflead of the 
Ordinary Gounterpoife (of Brafs ) employ one of Gold, or at 
Icaft of Lead, whereof the latter being of equal weight with 
Brafs, is much lefs in Bulk, and ih^ former amounts not to half 
itsbignefs. 
Thirdly y Thefe paxts of the Ballance, that may be made of 
Copper or Brafs, without any prejudice to the exadinefs, will, 
by being made of one of thofe Mettals, be lefs fubjed:, than 
Steel, (which yet, if well hardned and polifli'd^ may laft good a 
great while) to ruft with long ftandiug. 
Fourthly, Inftead of the fcales, the Buble may be hung at one 
end of the Beam, and only a Gounterpoife to it at the other, that 
the Beam may not be burthen'd with unneceffary weight. 
Fifthly, The whole inftrument, if placed in a fmall Fram,e, 
like a fquare Lanthorn with Glafs-windows, and a hole at the 
top for the Commerce of the internal and external Air, will be 
more free from duft, aud irregular agitations ; to the latter of 
which, it will otherwife be fometimes incident. 
Sixthly This inftrument being accommodated with a light 
^ Wheele and an Index ( fuch as have been applyed by the excel- 
lent Dr. Chr, Wren to open Weather glalTes, and by the inge- 
nious Mr. Ho@\to Baro(copes) may be made to Ihew much more 
minute variations, than otherwife. 
Seventhly, And the length of the Beam, and exquifitnefs of 
the BallanjCe, may eafily, rvith&ut any of the foregoing helps 
(and muc^h morexp^V/^ them) make the inftrument farexadier, 
than any of thofe, I was reduced to employ. And to thefe 
Accommodations divers others may be fug^efted by a farther 
confideration of the nature of the thing, and a longer prafti ce. 
Though in fbmerefpe<9:s this^y/^^^/WBarofcope be inferior 
to the Mercurial; yet in others it has its own advantages and 
conveniencies above it. 
And I.- It confirms oculum owr former Do(ftrine, that the 
falhng and rifing of the Mercury depends upon the varying 
weight of the Atmofpheres fince in this Barofcope it cannot 
be 
