MicrROGRAPHIAs 
Nor is this kind of Grain; asI may call it, peculiar to Glafs dropsthus 
quenched; for ( not tomention Coperas-ftones , and divers.other Adar- 
chafites and Adinerals , which I have often taken notice of to be: injthe 
-very fame manner flaked or grained, with a kind of Pithin the middle.) 
Ihave obferved the fame in all manner of caft Iron , efpecially the coar- 
‘fer fort, fuch as Stoves, and Furnaces, and Backs, and Pots are madé.of 
For upon the breaking of any of thofe Subftances it is cbvious: t6 -ob- 
ferve, how from the out-fides towards the middle, there is:a kind of 
Radiation or Grain much refembling this of the Glafs-drop;, but this 
Grainis moft con{picuous in Iron-bullets , if they be broken: the, fame 
Phenomena may be produced by cating regulus of Antimony into 
aBullet-mold, as alfo with Glafs of Antimony, or with almoft:any. fich 
kind of Vitrified fubftance, cither caftinto a cold Mold or poured into 
Water. 
Others of thefe Drops I heat red hot in the fire,and then fuffered them 
to cool by degrees, And thefe I found to have quite loft all their fidui- 
nating or flying quality, as alfotheir hard, brittle and {pringy texture; 
and to emerge of a much fofter temper, and much eafier to be broken or 
{napt with ones finger;but its {trong and brittle quality was quite deftroy- 
ed, and it feemed much of the fame confiftence with other green Glafs 
well nealed in the Oven. 7 | 
The Figure and bignefs of thefe for, the moft part was the fame with 
that of the Figure Z; that is,all the furface of them was very {moothand 
polifht,and for the moft part round, but very rugged:or knobbed. about 
1D, andall. the length of the {tem was here and there pitted or flatted, 
About D,. which isat the upper part of the drop under that fide of the 
{tem which isconcave, there ufually wasmade fome one or more little 
35 
Hillocks or Prominences. Thedrop it felf, before it be broken, appears | 
very tranfparent, and towards the middle of it, to be very full of {m 
Bubbles, of fome kind of aerial fubftance, which by the refraction of th 
outward furface appear much bigger then really they ares and thisma 
be in good part removed, by putting the drop under the furface of clear 
_ Water, for by that means moft part of the refraCction of the convex Sur- 
face of the dropis deftroyed, and the bubbles will appear much {maller. 
And this, by the by, mindsme of the appearing magnitude of the aper- 
ture of the7ris, or pupil of the eye, which though it appear, and be there- 
fore judged very large, is yet not above a quarter of the bignefs it ap- 
pears of, by the /evticular retraction of the Cornea. _tadsons 
_ The caufe of all which Phenomena Limagine to be no other then this, 
That the Parts of the Glafs being by the exeeflive heat of the fire kept 
off and feparated one from another, and thereby put into a kind of {lugs 
gith fluid confiftence , are fuffered to drop off with that heat or agitation 
t 
remaining inthem, intocold Water; by whichmeansthe outfidesofithe 
drop are prefently cool’d and crafted, and are thereby made of, a loofe 
texture,becaufé the parts of it have not time to fettle themfelves leifurely 
together , and foto lie very clofe together: And the inaermoft:parts.of 
the drop, retaining ftill much of their former heat and agitations, rémain 
G2 of 
