■( ^94r ) 
Cra^n^ V^^^^^J^g -^^ ^hefort geiierally (old at Toy fhops/ 
Tht I bne whereon they dropt was a round flat piece of 
folid Glals, r out nnioch thick, and over 5 whofe up- 
per lul^ce s well Grownd and Poliftit, It was fix'd in^a 
Tfn f ra itriv d on porpofe to keep its lower furface 
from beio- v ootigUQUs to the Plate or Leather, on which 
the F^ecipi nt was plac d ^ (which I mention purpofely, 
left any Gentlemen, who may have the curiofity to re- 
peat thefe Experiments, fhould fall intoanerror I very nar- 
rowly efcap'd) for when lirft I made thefe Experiments 
I iisy. a':Stpne::Plan2laid.}Cafiekfly .on the Leather that co- 
ver d the Plate, over which the Recipient being plac'd, 
and the Air exhaufted^ the defcending Marbles would 
not rebound fo high by an inch, as when the Experiment 
came to be made on the fame Plane in common Air 
which un.-^xpefted Piaasnomeoon gave great MOibrage that 
it might(iproceed frjom fbme unheeded caufe>, and (evera! 
reafoos w^re alledg'd againft the candour of the Experi- 
ment 5 th^ pfiocipal of which was, that the fwelling of 
the Leilhe^ ife vacuo raifed the ineumSeni Plane, caullng 
it- to lye -.n^c^re hollow and foft .than it.'did in . the open 
Air^ , Ia <?>i:d^r:'^h4refpre to,ieti true 
jighc, J-p'j^oeuredth-e.prieiiieBtioned G!afsPkne^;,.on which^ 
when I came (as before) to drop the Marbles, their Refi- 
lition then was fomething more m Vacnotlim in common 
Air (which put it pall: all doubt, that theFJrror proceeded 
from the caufe faggefted. ) Thofe dropt in common Air 
had likevvife fonie fniali advaotage in t'beir rebound^ above 
thofe let fail in Air condeafed. The Condcnfation be- 
ing but one Afmofphere, not daring to venture more, the 
breaking of the Recipient being very hazzardous. The 
Refilition of the Marbles from th^^f^'lane in fe^^? Was a- 
boUt lol inches, whicfc was fdmething'm^re t hatt | of their 
defcent. In Gondenfed Air their re&^uiid is^as a'bout 10 
inches. Accordingly we muft account their Refilition in 
Common Air to be the medium of the other two, it being 
difficult 
