( $i6o ) 
i^gExmB of Letters from Dr. John Wallls U the TuhlifinT 
i677St^t.76.%ic^ concerningthe Su^enpn of ^t^k^ftluer 
well purged of Air^ much higher than the ordinary Standard 
in the TorriceBian Experiment. 
S I R, 
I Am not forry to find 5 in your TranfaSions for the laft 
Month,(which 1 have tacwlf received,) that M,H»gmr 
aa logeoious and loquifitive perfon ^ doth endeavour to 
give a.Reafon of that Odd phenomenon in the Torricellian 
EKpcriment(obferv'd by my Lord Brounc^r^and Mr. Eojle^ 
many years (^ocej in purfuance of an Order of the R.society 
to that purpofej) of which I give an account in ray Treatife 
DeMotnCapa^^Schol.prop.i^. The Phsenomenon is this: 
Whereas in the Torricellian Experimentjthe Quicklilver 
contain'd in the Inverted Tube, how long foevcr^ whofe q* 
pen orifice G. is imraerged in ftagnant Quickfilver, does 
Ti£. ufually fall down to the height of about 29^ inches above 
the furfaceof the ftagnant Quickfilver AB , and there re- 
mains fufp€nded,as at I: If the Qiiickfilver be well cleans'd 
from Air, it has beed found to ftaod top-full, much higher, 
even to the height of 75. inches (and how much higher it 
may ftandj we cannot tell 5) but upon the admiflSon of the 
kftAifj or a concuffion of the Tube, it falls down to the 
ulual ftandard. 
^ Two Rcafons I did there hint ( though not perfeftly fa- 
tisfied in eitherOThet^^e^of my ownjconcerning the Spring 
of the Airs neeeffary to put Heavy bodies in motiooy not 
itnpeird by any other force : The other.ofmy UBrmncker^ 
that there might be in the Air yet a greater Weight or Pref- 
fure than is neceffary for the height of 29 inches, in cafe 
there be nothing but the bare weight of Quickfilver to be 
lupportcd. 
I find, Monfieur Hugens to fall in with that of my Lord 
BroHncker, fave that what we comprehend under the oame 
^ Air.htcMs^ more fubtik Matter: which alters not the 
We at alJ^ but only the Name. 
By 
