32 
MicROGRAPHIA. 
by fome {mall heterogeneous agil part of the Water, or Air, or Quick: 
filver; which appears like a bubble, and by its jumbling to and fro there is) — 
made way for the heterogeneous ther to obtrude it felf between the — 
Glafs and either of the other Fluids, the Gravity of Asercury precipitates 
it downward with very great violence ; and if the Vefiel that holds the 
reftagnating Afercury be convenient, the Mercury will for a time vibrate to 
and fro with very large reciprocations, and at laft will remain kept up by 
the preffure of the external Air at the height of neer thirty inches. And 
whereas it may be objeGted, that itcannot be, that the meer imbod ying 
of the Zther between thefe bodies can be the caufe,fince the Zther has 
ving a free paffage alwayes , both through the Pores of the Glafs, and 
through thofe of the Fluids, thereisno reafon why it fhould notmakea _ 
feparation at all times whilft it remains fufpended, as when it is violently 
difjoyned by a fhog. TothisI anfwer, That though the ther paffes — 
between the Particles, that is, through the Pores of bodies, foasthat any 
chafme or feparation being made , it has infinite paflages to admititsen- 
try into it, yet fuchis the tenacity or attractive virtue of Congruity, that — 
tillit be overcome by the meer f{trength of Gravity, or by a fhog afiifting — 
that Conatus of Gravity, or by an agil Particle, that is like aleaver agis 
tated byt 
he almoft contiguous Particles of the Fluid , and fuffers them not tobe ® 
feparated, till by meer force that attra¢tive or retentive faculty be over- 
come: But the feparation being once made beyond the Sphere of the — 
but the Azercury freely falls downwards till it meet witha refiftance from 
the preflure of the ambient Air, able to refiftits gravity, and keep it for- 
ced up inthe Pipe tothe height of about thirty inches. 
Thus have I gently raifed a Steel pendulum by aLoadftone to a great — 
Angle,till by the fhaking of my hand I have chanced to make.a fepara> 
tion bétween them, which is no fooner made, but as if the Loadftone had — 
retained no attractive virtue, the Pendulum moves freely fromit towards — 
the other ‘fide. So vafta difference is there between the attractive vir- _ 
‘tue of the Adagnet when it acts upon acontiguous and upona disjoyned — 
body : ‘and much more muft there be between the attractive virtues of 
congruity upon a contiguous and disjoyned body 3 and in truth the attra: 
ctive virtue Is fo little upon a body disjoyned, that though have with a 
Microfcope obferved very diligently, whether there were any extraordi- _ 
nary protuberance on the fide of adrop of water that was exceeding neer — 
to the end of a green ftick, but did not touchit, Icould not perceive the © 
leaft; though I found, that as foon as ever it toucht it the whole drop — 
would - prefently unite it felf with it; fo that itfeems an abfolute con- — 
tact isrequifite to the exercifing of the tenacious faculty of congruity. 
“ Obferv. 4 
he #tber 3 and thereby the parts of the congruousfubftances 
ated fo far afnder , that the ftrength of congruity is fo farwea- 
ned,as not to be able to reunite them, the parts to be takenhold ofbes 
ing removed out of the attractive Sphere, as may fo fpeak; of thecon — 
gruity; fuch, Hay, isthe tenacity of congruity, that it retains and holds 
_attrattive activity of congruity, that virtue becomes of no effect at all, 
