( 79 ) 
Which ftems to be in effefl the fame with what the Honourable 
Rolpert Boyle wichciearnefs teacheth in his Hydrojtatical Let- 
ter^ printed^. i672.upon theoccafion of fjme Exceptions 
made by Mr. Sinclair about a Way oi Weighing tvaterin watery 
where he faith, that the upper portion of warer does really 
/>r<f/thefubjacent,though it doth not afliially Aeprefi it ; or, 
6oi\\ gravitate on it,but not pra-gravitate. Mean time, this Au- 
thor here pretends to prove the faid non-preffing of water up- 
on water both by Reafon and Obfervarion. After which he 
examins, whether the free andcommon Air, wherein we livc^ 
(commonly czWtdAtmofphere^ extending upwards about feven 
miles or more, hath any lenfible aflual Gravitation upon the 
lower world *, and admit it have, whether any determinat por- 
tion of that Atmorphere,as a Column or inverted Cone,for the 
purpofe of fix inches fquare at the bafe, hath any aflual gravi- 
tation upon the fubjefled bafe,on which it is fuppos'd to reftg 
and fuppofing it have, whether that gravitation be of any con*» 
fiderable,andof what, moment? Where he deniethnot, that 
Air cmprefs'd may have w^eight in it,ro as to gravitate confide- 
rably upon other Alr,either not at all,or lefsjcomprefs'd; nor, 
that eventhe/re'Mir itfelfmay have fome intrinfyue gravity, 
though exceeding little *, nor,that this free Air nvay have fome, 
though very inconfiderable^ meafure of a0ual gravitation , 
which yet he thinks is icarce perceptible to fenfe,notwithftan- 
ding all the mixtures ofvapors and fleams from the Earth and 
Water. But that which he labors to maintain, is, i. That the 
whole body of the Atmofphere hath no cmftierable Gravitati- 
on either upon its own pans, or upon the fubjefied body of 
the Terreftrial globe, much lefs fuch a notabk gravitation, as 
is fuppofed by thofe hedifputes againft, 2- That, if it had, yet 
any given portion or Column of the Atmofphere hath no fuch 
gravitation. Concerning the/^;^z»^'r, he thinks fit to fay little, 
referring himfelf therein toFrancLinm hisTrafl: de Infeparabi- 
litate Corporum^ and to Hon.Fabri in the fixth of his late FMlofc 
Conferences and he fcr up! es not to fay, that there is not any 
Inftance or Experiment, known to him, andallcdged for the 
evincing of that pretended Gravitation of the free Air, but is 
readily capable of a more futable Solution, more adequately 
fitted 
