( io88 ) 
in the Tube may be fuftain d by the difterence between 
thofe two Preflures. This Explication Teems to be fa* 
vour’d by the following Experiments, which may all be 
accounted for in the fame manner, though I fliall anon 
mention another Caufe, which contiibutes to the Suc- 
eeXs-of the firft and (econd. 
The lirft I (hall mention, is the famous Experiment 
of the fulpenfion of Mercury purged of Air, to the 
height of 70 or 75 Inches, in the Tcrrktllian Tube, in 
the open Air. To which we may add the fuftaining 
of Mercury likewife purged of Air within the exhauft- 
ed Receiver, as related by that Learned and Succefsful 
Promoter of. Natural Knowledge, Moof. Papin, in his 
Continuation du Digefteur. 1 forbear to mention the 
furpenfion of Water purged of Air, in the Vacuum, 
which he deferibes in the fame Book 5 becaufe there is 
little difference between that Experiment and oar own 
abevementioned, the very tf p of the arched part of his 
Tube, which top we may fuppofe as fmall as W’e pleafe, 
(applying the place of the fine Capillary at the top of 
our Tube. ' But we mufl: not mnit the Experiments 
made by the famous Monf Huygens^ and defenbed by 
him in Phil. Tranfaci. No 8^. of the cohering of po- 
lifh’d Plates with a confiderable force in the exhaufled 
Receiver; as likewife of the running of Water and Mer- 
cury, when purged of Air, through a Siphon of une- 
qual Legs in the Vacuum : All which he accounts for 
from the fame Principle, and much in the fame manner, 
as we have ufed for explaining the Experiment above. 
• As to the Exiflence of fuch a Medium, ! lhall con- 
tent my felf to refer to what has been (aid by our //- 
l' 4 ^ricus Preftdent in the Queries at the latter end of 
the laft Edition of his Opticks : and as 1 have lately 
had the Honour to entertain the Society with fome Ex- 
periments upon Quickfilver, which were exadly the 
reverfe 
