( 7«S ) 
wliich fell to the Bottom at the fame InBant of Time : 
Now fince the chief Refifiance of a Medium ( and in- 
deed almoft all of it ) depends upon the f Quantity 
. of its Matter 5 therefore this Diminution of Refiftance, 
whereby the Feather fell as Toon as the Guinea, fliew’d 
a Diminution of the Quantity of Matter, and conle- 
quently prov’d an interfpers’d Vacuum. Some time 
after this, I was inform’d that fome here in 
England objeded againft the i hormefs of the Glafs-Re- 
-ceiver; as if the Difference of Time in the Fall of the 
two Bodies, which they affirm’d to be real, could not 
be perceiv d in fuch a Glafs ; and that lome Philofb- 
phers from abroad affirm’d that in a Glafs Receiver 7 or 
8 Foot long, there would be fuch a manifeft Difference 
in the Time of the Fall of the faid Bodies, as to fhew 
this Experiment no Proof of a ^ ncuum ; though at the 
fame time, Tome of the Objedors well knew that there 
- could be no Receivers of half that Length made at 
the Glafs Houfe, and therefore thought the Experiment 
impradicable. To obviate this, I contriv’d a Machine 
for the purpofe, which confifted of a flrong wooden 
-Frame 15 Foot high, that held the Air-Pump and four 
Cylindric Glafs-Receivers of about two Foot long each, 
and fix Inches Diameter Of thefe, having fet the firft 
upon the Air-Pump Plate, I laid on the Top of it a 
Brafs-Plate of feven Inches Diameter, that had an oil’d 
Leather fix’d to it above and below, with an Hole 
through the middle, of between four and five Inches 
Diameter; then on that Plate I fet the next Receiver, 
with a like Plate at top; and after the fame manner 
fix’d the other two with Plates between them : The 
upper Receiver being a little narrower at the Neck, 
t See Sir //i Brinci^ia, Book II- Prop. 4o. 
went 
