AA MicrRoGRAPHIA, 
Schem, Se 
before they were {0 exceeding hard,that they could not be broken with 
out much difficulty; and upon their breaking the whole drop’ would 
fly in pieces with very great violence. The Reafon of which laft feems 
to be , that the leifurely heating and cooling of the parts does not only 
waft fome part of the Glafsit felf, but ranges all the parts into a better 
order, and gives each Particle an opportunity of relaxing its felf, and 
conféquently neither will the parts hold fo ftrongly together as before, 
nor be fo difficultto be broken: The parts now more eafily yielding, 
nor will the other parts fly in pieces, becaufe the parts have no bended 
Springs, The relaxation alfo in the temper of hardned Steel, and ham- 
mered Metals. by are them inthe fire,feems to proceed from much the 
fame caufé. For both by quenching fuddenly fuch Metals as have vitri- 
fied parts interfpers’d, as Steel has,and by hammering of other kinds that 
do not fo much abound with them, as Silver, Brafs, Gc. the parts are put 
into and detained in a bended pofture , which by the agitation of Heat 
are fhaken, and loofened, and fuffered to unbend themfeélves, 
ieee i S. Pa a 
a a te : : . iat 
-sOblerv. VIN. Of the fiery Sparks firnck, from a: Flint or 
r= 
Steel,to make certain fiery and fhining Sparks to fly out from between 
e'two comprefling Bodies. About eight yearsfince , upon cafually 
I" is 2 véry common Experiment , by ftriking with a Fliat againft a : 
reading the Explication of this odd Phenomenon, by the moft Ingenious 
Des Cartes, Lhad agteat defire to be fatisfied , what that Subftance was 
chat gave fuch a fining and bright Light : And to that end fpread a 
fheet of white Paper,and on it, obférving the pe where feveral of thefé 
Sparks feemed to vanith, I found certain very fmall, black, but gliftering 
Spots of a movable Subftance, each of whith examining with my Mifero- 
cope, found to bea final] round Globule 5 fome of which, astheylooked 
prety fall, fo did they from their Surface yield a very bright and ftrong 
reflection on that fide which was next the Light; and each look’d almolt 
like a prety bright Iron-Ball, whofe Surface was prety regular, fuchasis — 
reprefented by the Figure A. In thisT could perceive the Image of the 
Window prety well, or of a Stick, which I moved up and downbetween _ 
the Light and it. Others I found,which were, as to the bulk of the Ball, 
pasty regularly round,but the Surface of them,as it was not very iia E 
ut rough,and more irregular, fo was the reflection fromit more faint and 
confuled. Such: were the Surfaces of B.C.D. and E. Some of thefel — 
found cleft or crackéd, asC, others quite broken in two and hollow, a8 
Db. which feemed tobe half the hollow fhell of a Granado, brokenirre- 
gulatly in pieces. Several others I found of other fhapés; but that — 
which is reprefented by EF, I obferved to ‘be a very big Spark Bt ES = 
which Went out upon one fide of the FlintthatI ftruck fire withall; to 
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