\ 
ADefcription of an Jn^umtion^ rvhenhy the Di'vifions of 
the Barometer may be enlarged in any gi^en proporti- 
ons\ produced before the Roy all Society^ by Mr. Robert 
Hook K.S. Soc, and ?r(fefs. Geom. Grcfliam. 
Since the dilcovery of the Alterations, that are in thefc 
parts ot the World, in the weight of the Amoffhere^ 
by trie means of the Torricellian Tuhy there has been ftve- 
I rai contrivances thought on, to make the more minute va- 
j ^iations in the Airs prelTure fenfible. 
And firft, the Whcd-Baromaer was invented and Pubhlli- 
ed by Mr. Hook^ Anno 1665, in his Micrography : ( where it is 
, defcribed at large^ but this did not anfwer fully the defign- 
cd exadnefs, both for that the Mercury being apt to ftick 
againft the fides of the Glafs, would rife and fall fdturj^^ 
all at once, and becaufe it is very difficult to adjuft the Ball 
and Thread and other apparatus of this Infl:runient, as alfo 
lhat it is exceeding apt to be out of order, for which reafbn 
it is at prefent almoft wholly laid afide. 
Upon this in Ju/^e 1668 ( as appears on the Journal 
oftheRoyalSociety /he bethought himielf of an other de- 
vice to do the fame thing, which was to cncreafc the divifi- 
ons by putting coloured Spirit of Wine,or fbme other Liquor 
not capable of Freezing,on the Mercury, which Liquor was 
fcinade to rife as the Mercury fell,and fall as it r jfe,in a narrow 
Cane, fo as to make the utmoft limits about two foot afun- 
' ^er. This Invention was afterwards in the Year 1673 Pub- 
Jifhed in Fraftce by Mv.Hdi^^y who neatly performed the 
Glafs-work; but the Cane being necelTarily Irnall and apt 
to be be obftruded with bubbles, ( whereby the intercourfe 
of the outward Air would be intercepted j and befides the 
I utmoft limits of rife and fall fcarce reaching two foot and a 
I half, Mr. Hook was not yet fatisfied, till he had found out 
the 
