178 A SYSTEM OF 
requires an explanation, fmce the author in his: 
description does not obferve the necelTary diftinc- 
tion between alcali and lime j and quotes the horn 
filver ore, and the luna cornea^ as proofs of his 
opinion *, by which, however, his opinion feems 
lather weakened than confirmed. 
SECT. CLXXIX. 
3. Platina del Pinto, Platina di Pinto, Juan 
hlanca, n 
This metal is a recent difcovery of our 
times, and is defcribed with great accuracy 
by Scheffer, in the A6i:s of the Royal Aca- 
demy of Sciences at Stockholm, for the year 
1752; as alfo by Dr. Lewis, in the Phiiofo-^ 
phical Tranfadlions for the year 1754, voL 
xlviii. And though thefe two gentlemen 
agree in the principal circumflances relating 
to this metal, yet it is very plain by their 
defcriptions, that neither of them knew any 
thing of the other’s experiments. By thefe 
defcriptions we are convinced of the refem- 
blance this metal bears to gold •, and there- 
fore we muft allow it to be called white gold^ 
though, both theoretically and pra^lically, it 
may be diftinguifhed from gold by the fol- 
lowing qualities. 
1. It is of a white colour. 
2. It is fo refractory in the fire, that there is 
no degree of heat yet found by which it 
can be brought into fufion by itfelf, the 
burning-glafs excepted, which has not yet 
been tried. But, when mixed with other 
metals, and femi-metals, it melts very 
eafily, and efpecially with arfenic, both in 
its 
