i82 A SYSTEM OF 



j, i. In larger grains ; and, 

 2. In fmaller grains. 



SECT. CLXXXII. 



2. Tin mixed with the calx of iron. 

 Sect, lxx. 



3. Tin mixed with the manganefe. 

 Seel;, cxvii. 



4. Tin mineraliied with fulphur and 

 iron, black lead. Sect, cliv. 



SECT. CLXXXIII. 



Observations on Tin. 



It has indeed been afferted 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 ken. a fingle fpecimen that could be 

 called 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 m England and Saxony. It is likewife 

 worthy obiervation, that when its ore is profitable, 

 or to be worked to any advantage, it is always in 

 form of an indurated calx, which anfwers to thole 

 glaf-cs that are prepared from metallic calces in 

 our laboratories : Therefore, in regard to this re- 

 femblance, as well as to what this Mineralogical 

 Enay requires from its readers, I have ufed the 

 term calx, in describing the metals ; by which word 

 is underilood the fame as the chemifts call a crocus, 

 or terra met allorum phlogiftc privqta. 



The tin mud, however, be mineralifed with 

 fulphur in the black lead; but the quefcion is, 

 whether that would have happened if the iron 



had 



