( 226) 
great eafe and fpeed ; and by it I have performed fome things upon 
Minerals and Mettals, which with crude Antimony alone I could 
not cfFeft. 
Take of Antimony one pound ; flux it clear ; Have an ounce or 
two ofche Cawk-ftone (by and by to be defcribed J in a lump red- 
hot in readinefs. Put it into the Crucible to the Antimony ;continue 
the flux a few minutes: Caft it into a clean and not greafed Morcar, 
decanting the melted liquor from the Cawk. 
This Procefs gives us above 1 5 ounces of njitrum of Antimony y 
like polifti't Steel, and as bright as the mod refined Quickfilver. 
The Cawk feemsnot to be diminifli't in its weight, but rather in- 
creafed; nor will be brought to incorporate with the Antimony, 
though flux't in a ftrongblaft. 
This Cawk-ftone is a very odd Mineral,and I always looked up- 
on it to be much a kin ro the white milky Mineral juyces,! formerly 
fent you a fpecimen of: And this Experiment is demonftrative,that I 
was not miftaken ; for, the milky juyceof the Lead-Mines vitrifies 
the whole body of Antimony in like manner. 
That this Vitrification is from thtproper nature of Cawk, I little 
doubt ; for, I could never light upon any one mineral fubftance, 
which had any fuch effeft upon Antimony ; and I have trycd very 
many, as Lapu Calaminaru, Stone-Sulphur or Sulphur vivum^Gala- 
Bites, Sulphur Marcajite^ AUom-glebe, divers S^^m, &c. 
Cawk is a ponderous white ftone,found in the Lead-Mines^it will 
draw a white line like Chawk or the GaUSlites : And thongh it be 
fofree, that it is more firm, and hath a fmooth and fliining grain, 
Sparr-like,yet not at all tranfparent. Of the Spirit,it yields by di- 
ftillation,another time. lam, 
Tprk^ Novemb.2o» 1674» Sir, Your, e^e. 
An Accompt of fome Books, 
I. TRACtS^containing i.Sufpicions al^out fome Hidden Qu^\k]escf 
the Air, with an Appendix touching Celeftial Magnets, and fome 
ther particulars^ 2. Animadverfions upon Mr. Hobbs'/ Problemara 
de Vacuo. ^,A Difcourfe of the Caufe of Attraction by SuCticn: By 
the Hor^ourable ROBERT BOYLE Efq^Fellm &fthe R.Sociecy, 
London, 1674. 8^ 
TN ihe firji of thefe Trafts^the Noble Author, pafling by thofe ob- 
vious Qualities of the Air, Heat,Cold,Drynefs^v\d Moijlure.^nd 
fuch others, as are now alfo well enough known, I mean, Gravity^ 
Springynefs^RefraC}ivenefs,8cc^eviquiTesmto^znd delivers his Con- 
K flures about, fome yet more Latent ones. And the chief account, 
upon 
