( V66 ) 
matter than Air doth without difficulty penetrate Gb(s, 
Water, Quickfilvcr, and all other bodies , which we find 
impenetrable to Air 5 I know not whether he mean,without 
any difBculty (as the words feem to import,) or (as I con- 
jefturc by what follows) without ^re^^ difficulty, though 
with fome. 
But his Lordfhip (iflroiftake not) though he allow his 
(SpriDgy)Subtile matter to penetrate Glafijyct not without 
difficulty-andstill it have (bme room made(as HD)whereia 
it may recolleft it ielf, cannot exert its Spring , and there- 
fore not while top-full of cleanfed Quickfilver, but, fo 
foon asfomeroom is made forit : Whereas, iftheQuick-^ 
filver be not purged of Air, that little Air remaining doth 
by Its Spring begin the motion. 
He thinks it alfo not improbable ( and if it fo prove , it. 
will be a good confirmation of this Hjpothtfis,) that a large 
but low Tube of Glafs (fiiorterthan 29 inches) may ftand 
top-full of Quickfilver, though with a fmall hole in the 
Top, as at K ; at left, if immerged in Water, in cafe Air be 
too Subtile for our Mechanicks. 
He might alfo , fuitably enough to his own Hypothefis,, 
have fo explained himfelf, as to allow his more Subtile 
parts of common Air to penetrate Quickfilvcr, but not 
Glafs 5 and therefore, in cafe of room for it at HD,it might 
through the Stagnant Quickfilvcr 5 and. that at C, pafs up- 
wards to HD, and there exert its Spring, 
I fball forbear to difpute againft this Hypoihcfisfor the 
prefect j bccaufe I think it more proper to examine by Ex- 
periment (which I think hath not yet been done,) whether 
well-purged Quickfilver may not be made to ftand higher 
than C I, the ordinary ftandard, fuppofe at CHjWith a void 
fpace about it, as HD. For the ifliie of this Experiment (a- 
mongft others to be after mentioned,)feems very proper for 
determining of this doubt 5 which therefore I am not wil- 
ling to pre-judgCi There is yet another way of explicating 
the fame Hypothefis, without allowing this Subtile matter 
to pierce the Glafs 5 which is this : 
Oui: 
