A SYSTEM OF 
1. In larger grains ‘ and, 
2. In fmaller grains. 
SECT. CLXXXIL 
2. Tin mixed with the calx of iron. 
Sedt. Ixx. 
3. Tin mixed with the manganefe. 
Se6l. cxvii. 
4. Tin mineralifed with fulphiir and 
iron, black lead. Sed. cliv. 
SECT, CLXXXni. 
Observations on Tin. 
It has indeed been alTerted by fome, that Tin 
is found native in the earth but, for my own 
part, like many others, I doubt much of it, hav- 
ing never feen a fingle fpecimen that could be 
piled native tin. ’ It is, however, remarkable that 
tin is fo fcarce, and is not found in any confider- 
able quantity or purity in any other places in Eu- 
rope than in England and Saxony. It is likewife 
worthy obfervation, that v/hen its ore is profitable, 
or to be worked to any advantage, it is always in 
form of an indurated calx, which anfwers to thofe 
glaifes that are prepared frorn metallic calces in 
our laboratories : Therefore, in regard to this re- 
femblance, as well as to what this Mineralogical, 
' Eflay requires from its readers, I have ufed the 
term calx^ in deicribing the metals ^ by which word 
is underfcood the fame as the chemifls call a crocus^ 
or terra metallorum phlogifto privata. 
The tin mufc, however, be mineralifed with 
fulphur in the black lead ^ but the queftion is, 
whether that would have happened if the iron 
'■ ' ■■ ^ had 
