52 
MicROGRAPHEA., 
Sixthly, That any Iron may, in‘a very little time, be cafe hardned, ds 
the Aikiesdhen call it, by cafing the iron to be hardned with clay, and 
putting between the clay andiron a good quantity of a mixture of Urize, 
Soot, Sea-falt, and Horfes hoofs (all which contein great quantities of Sa- 
line bodies) and then putting the cafe into a good ftrong fire, and keep- 
ing it in aconfiderable degree of heat for agood while, and afterwards 
heating, and quenching or cooling it fuddenly in cold water. ~ | 
Seventhly, That all kind of vitrify'd fub{tances,by being fuddenly cool'd, 
become very hard and brittle. And thence arifes the pretty Phenomena 
of the Glaf! 
place. | 
Eighthly, That thofe metals which are not fo apt to vitrifie, do not ac+ 
quire any hardnefs by quenching in water, as Silver, Gold, &c.' 
Thefe confiderations premis’d, will, I fuppofe, make way for the more 
-eafie reception of this following Explication of the Phenomena of hardned 
and temper'd Stee]. That Steel is a fubftance made out of Iron, by means’ 
Drops, which I have already further explained in its own 
of a certain proportionate Vitrification of feveral parts, whichare focu- 
rioufly and proportionately mixt with the more tough and unalter’d parts 
of the Iron, that when by the great heat of the firethisvitrify'd fub- 
ftance is melted, and confequently rarify'd, and thereby the pores of 
the Iron are more open, if then by means of dipping itin cold water it 
be fuddenly cold, and the parts hardned, that is, {tay'd in that famede- _ 
gree of Expanfion they were in when hot, the parts become very hard 
and brittle, “and that upon the fame account almoftas {mall parcels of _ 
glafs quenched in water grow brittle, which we have already explicat- 
ed. If after this the piece of Steel] be held in fome convenient heat,till by, 
degrees certain colours appear upon the furface of the brightned metal, — 
the very hard and brittle tone of the metal, by degrees relaxes andbe- _ 
comes much more tough and foft; namely, the action of the heat does. 
by degrees loofen the parts of the Steel that were before ftreached or fet 
atilt as it were, and ftayed open by each other, whereby they become 
relaxed and fet at liberty, whence fome of the more brittle interjacent 
parts are thruft out and melted intoa thin skin onthe furface ofthe Steel, _ 
which from no colour increafes toa deep Purple, and fo onward by thefe- 
gradations ox confecutions, White, Yellow, Orange, Mininm, Scarlet; Purple, — 
Blew Watchet, &c. and the parts within are more. conveniently,and pro- 
portionately mixt; and fo they gradually fubfide into atexture which — 
is much better proportion’d and clofer joyn'd, whence that. rigidnefle — 
of parts ceafes, and the parts begin to acquire their former. dxdil- 
nefi. 
pee and rubb d off,the metal underneath it is white 
ept fis in the fire, fo as to increafe toa confiderable thicknefs,. it 
lows, be beaten offin flakes. . This is further confirm'd by this _ 
may, by 
oblavable, that that Iron or Steel will keep longer from rufting whick 
is covered with this vitrify'd cafe : Thus alfo Lead will, by degrees, - 
Now,that.’tis nothing but the vitrify'd metal that fticks uponstiedeaface ; 
of the colour'd body, is evident from this, that ifby aay means it:be fcra-_ 
and clearsand.ifit be 
