t 5 86 ] 
by a Semi metal brought from the Weft Indies , 
whereof I have now the Honour to prefent Speci- 
mens to the Royal Society. And this Semi-metal 
feems more particularly to deferve our Attention, as 
it is' endu’d with fome very fmgular Qualities, which 
plainly demonfirate that certain general Theorems, 
tho’ long eftablifh’d, and univcrfally receiv’d by the 
Metallurgifts, yet do not hold true in all Cafes, and 
ought not to be admitted into their Arts, without 
proper Limitations and Rcflridions. For inflancc, 
That Gold and Silver may be purified from all he- 
terogeneous Sub fiances by .CoppeUution\ is a Propo- 
sition that ail A flayers and Renners have long thought 
true and undeniable; yet this Proportion ought not 
to be receiv’d by thofe Artificers, without an Excep- 
tion to the Semi-nacul here treated of; Alice, like 
thofe nobler Metals, it refills the Power of Fire, and 
the deflrudivc Force of Lead in that Operation. 
-t This Semi-metal was firft prefented to me about 
nine Years ago, by Mr .Charles Wood, a skilful and 
inquifitive Metallurgy, who met with it in Jamaica, 
whither it had been brought from Carthagena in 
Meva Spam. And the fame Gentleman hath fince 
gratified my Curiofiry, by making further Inquiries 
concerning this. Body. It is found in conftderable 
Quantities in the Spanifh Weft Indies (in what Part 
I could not learn) and is there known by the Name 
of Tlatina di Tinto The Spaniards probably call 
it Rlatina, from the Refemblance in Colour that 
it bears to Silver. It is bright and fhining, and of 
a uniform Texture; it takes a fine Polifh, and is 
not fubjed to tarnifh or ruft.j it is extremely hard 
and compad ; bur, like Bath-metal, or caft Iron, 
brittle, and cannot be extended under the Hammer. 
The 
