12 MicrROGRAPHIA, 
By Congruity, I mean a property of a finid Body, whereby any part of it 
it vedi sainaa with any other ran either of it felf, or of any other simi- 
bar, fuid, or folid body: And by Incongruity a property of a fad, by which 
it is hindred from uniting with any diffimilar, fiuid,or folid Body. 
This laft property, any one that hath been obfervingly converfant 
about fluid Bodies, cannot be ignorant of: For (not now to mention 
feveral Chymical Spirits and Oyls, which will very hardly, if at all, be 
brought to #ix with one another; infomuch that there may be found 
-fome 8.0r 9, or more, feveral diftinct Liquors, which fwimming one up- 
‘on.another, will not prefently #ix) weneed feek no furtherfor Exam- 
ples-of this kind in fluids, then to obferve the drops of raiz falling through 
the wir, and the bubbles of air which are by any means conveyed under 
the furface of the water 5 or a drop of common Salet Oyl fwimming upon 
‘water. In all which, and many more examples of this kind that might 
be enumerated, the ézcongruity of two fluids is eafily difeernable. And 
-as for the Congruity or Incongruity of Liquids, with feveral kinds of firm 
Bodies, they have long fince been taken notice of, and called by the 
Nainesof Drinefrand Adoifture (though thefe two names are not compre+ 
henfive enough, being commonly ufed to fignifie only the adhering or 
not adhering of water to fome other fold Bodies of this kind we may ob- 
ferve that water will more readily wet fome woods then others ; and that 
water, let fall upon.a Feather, the whiter fide ofa Colport; and fome 
other leaves, or upon almoftany dufly, unZuous, or refinous faperficies, 
will not at all adhere to them, but eafily tumble off from them, like a folid 
Bowl; whereas, ifdropt upon Linnen, Paper, Clay, green Wood, &c. it will 
not be taken off, without leaving fome part of it behind adhering to them. 
So Quick-filver, which wall very hardly be brought to fick to any vegeta® 
ble body, will readily adhere to, and mingle with, feveral clean metalline 
wdies, os . ; : ; AH 
And that we may the better finde what the caufe of Comernity and — 
Yncongruity in bodiesis, it will be requilite toconfider, Firft, what isthe 
caufe of fluidnefs; And this, Iconceive, to be nothing elfe but a certain 
poe or hake ot beat, for Heat being nothing elfe buta very briskandve- 
hement agitation of the parts of abody (as Ihave elfwhere made proba: 
bable)\the parts of a body are thereby made {0 /oof from oneanother; 
that they cafily move any may, andbecome flvid. That I may explain — 
this ‘alittle by a grofs Similitude, let us fuppofeadifhof fand fet upon 
fore body that is very much agitated, and fhaken with fome quick and 
frrong vibrating motion,as ona AMdilftone turn’d round upon the under {tone 
very violently whilft it is empty3or on a very ftiffDrwm-head,whichisve- 
hemently or very nimbly beaten with the Dromfticks, By thismeans, _ 
the fand in the dith, which before lay like adv/and una@tive body, be- 
comes a perfect fwd, and ye cannofooner make a hole in it with your 
finger, but itis immediately fied up agaim, and the upper furface of it — 
leoell'd. Nor can you bury a light body, asa piece of Cork under it, but 
it prefently emerges or fwims as ‘twere on the top; nor-can youlay a) 
heavier onthe top of it, asa piece of Lead, but it is immediately buried 
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