Microcraruia., 
_ obferved inithofe Bubbles which Childreii ufe to make with Soap-water, 
I did the lefs wonder 5 efpecially whenupon Experiment I found, ‘I was 
able to produce the fame Pheromenain thin Bubbles made with any 
other tranfparent Subftance. Thus have I produced them with: Bubbles 
of Pitch, Kofin, Colophony, Turpentine, Solutions of {everal Gums, as Gums 
Arabick i imwater; any glutinous Liquor,as Wort, Wine;spirit of wae, or 
of Turpentine, Glare of Snails; &e. © 
It would be needles to: enumerate the feveral Inikances thefet 
enough to fhew the generality or univeriality of this: propriety. rene 
muft not omit, that we have inftancesalfo of this kind even in metalline 
Bodies and animal ; for thofe feveral Colours which are obferved tofols 
low cach other upon the polifht furface of hardned Steel, ‘whenitisby a 
fufficient degree of heat gradually tempered or fofcened , are produced 
from nothing elfe but a certain thin Lawina of a vitrum or vitrified part, 
of the Metal,which by. that degree of heat, and the concurring action of 
the ambient Air,is driyen out and fixed on the furfaceof the Steeh 
And this hints to mea very probable. ¢ at leaft, if not the true) -caufe 
of the hardning and tempering of Steel, which hasnot, think; beet yet 
given,nor, that I know of, been fo much as thought of by any. And that 
1s this,that the hardnef of it arifes from a greater proportion of a vitrifi« 
ed Subftance interfperfed through the pores of the Stee]. And that the 
tempering’ or foftning of it arifes from the proportionate or finaller parcels 
of it left within thofe pores. This will ee the more ecties ahs we 
confider thefe Particulats. 
Firft, ‘That the pute parts of Metals are of themfelivess fexible 
anid buffs thatis,” will indure beridingy ad hathmering,and yetr i their 
conti 
“Next, "That the Patts of all vitrified Subftandes;: as all kinds of Glafy 
the Scoria of Metals, Gc: are very hard, and alfo'vety brittle; being nei 
ther flexdble nor malleable, but may by hammering or beating be byuked 
‘into {mall parts or powders: : 
‘Thirdly, That all Metals’ ( excepting Gold aid ives 3 ¥ Aphiet! hdr slot 
fo much with the bare fire, unlefs aflifted by other faline Bodies )' do 
more of lef witrife by the ftrength of “fire, thatis, are corroded by a fa 
line Subftance, which I elfewhere fhew to be the truecaufe of fire; and 
ate thereby, as by feveral other Azeh/truues,converted into Scoria 5 And 
this is called, calcining of them, by Chimifts) ‘Thus Iron and Coppe oe ih 
and quenching do turn all of them by degiees into Seoria, ie 
are evidently vitrified Subftances ; ahd unite | th GlaG , and are eafil 
Ppele s 5 and when cold, ‘very hard, and very brittle. 
‘Fourthly; That mrioft kin kind of Vitrific intone or Caleinations Bek 
‘uniting and iti ing ' wack the rtietalline Particles.» Nor dot 
know any one caleination y erheete ‘a Saline oot may’ hots “with? very 
eat’ probability, be faid to be ah agent or coadjutor. i 198 
ifthly, That Iron reenter er by teans of the acorn 
tion of certain ‘on, with which ic im kepescereein tine? in the ire. 
I 2 | Sixthly, 
br 
