f ^029 ) 
glafs, behind whifch they arc placed J they retain one a nother^ 
and they remain all fnfpended , becaufe there is much leis 
preffure on Che furface of the qarckfilver that is cootignous 
tothe glafs;, tkan upon that below^ which is all expofed to 
the ad:ionQf that matter which makes this fecondpreffure. 
The ingenious and candid Author of this folution acknow- 
kdgeshimfeIC that it doth not fo fully faCisfiehim as not to 
leave fome fcruple behindsbut then he adds,that that keeps him 
MOt from being very well aflTurcd of that newpreffure, which 
hehathfuppofedbefides thatof the Air, by reafon as'well of 
the Experiment already alledged^ as of two others^ which he 
fubjoins to this efFcd 3 
Firft, When two plates of mettal or msrble, whofefurfaces 
arc perfedly plain, are put one upon another^they do fo ftick 
together, that the uppermoft being lifted up, the undermoft 
follows without quieting it : And the caufe hereof is juftly ad- 
fcribed to thepreffure of the Air againft their two external 
furfaces^ He taking then two plates^each of them but about 
an inch fquare, being of that matter, of which anciently they 
made Looking- glafles, and clbfingfo exactly together, that 
without putting any thing between, the uppermoft keeps not 
only up the other, but fometimesalfo with it three pounds of 
lead fatten d to theiowermoft,and thus they remain together 
as long as you pleafe.Having thus joyned them and charged 
them with three pounds weight, he fufpended them in the 
Recipient of his Engio^ and exhaufted it of Air fofar as that 
there remained not enough to fuftain by its preflTure as much 
as an inch high of water ; and yet his plates disjoyned not^ He 
adds, that he made the fame Experiment by putting Spirit of 
Wine between the two plates 3 and found, that in the Reci- 
pient evacuated of Air they fuftain'd, without being fever'd, 
the fame weight they did when it was full of Air.This,he thinks, 
Ihews clearly enough, that there remains yet in the Recipient 
a prefTure great enough after that of the Air is thence 
taken away 3 and chat there is no more reafon to doubt of it, 
than of the preffure of the Air it felfl 
The Second E^j^cxxmtnt is , That whereas the effect of a 
fiphoaof unequallegs, by which you make the water of a 
veffel to run over^jis no longer adfcribed to a fuga vacui^ but 
C c c c 2 to 
