364 On Primary Ores of Iron. 



thefe fhall be, the ore of the ifland of Iflay, and the Cumber- 

 land iron-ore. 



Of the former I pulverifed 872 grs. which I threw into an 

 iron veffel of a red heat. In 1 i minutes, during which time 

 no fenfible fmell was difengaged, the powder affumed a com- 

 plete change of colour, and loft in weight 12 grs. The ore 

 was again returned into the furnace, and expofed to a bright 

 red heat for 5 minutes, in which time it loft farther 28 grs. 

 — in all 40 grs. = 4-58 per cent. 



I next reduced to fmall pieces 2700 grs. of this ore, and 

 ftibjefted them to a high heat for 8 hours, partially expofed 

 to air, in which time 314 grs. of volatile mixtures were 

 driven off, equal to n "i per cent. 



The ore had now affumed a reddifh blue colour ; had be- 

 come friable, and much divided ; it parted in fmall granulated 

 mattes, like the fragments of quartz, but was confiderably 

 magnetic. The fraclure was rough, full of afperities ; it 

 did not effervefce with acids, nor had it acquired any fenftble 

 increafe of weight; when pulverifed, the (hining fpecula 

 were moft confpicuous, and very magnetic. Some of their 

 furfaces, by avoiding the one pole of the magnet, and em- 

 bracing the other, led me to fuppofe they had polarity. In 

 order to de-oxygenate this ore, I introduced 2040 grs. in 

 fmall pieces, mixed with charcoal, into an iron teft luted 

 with clay, and expofed the mixture to a high red heat for 

 ten hours : the ore then feparated from the charcoal, and 

 •weighed, was found to have loft, of volatile mixtures and 

 oxygen, 456 grs. = 22*3 per cent.; from which deducting 

 j V% as the quantity of volatile mixtures, being the quantity 

 loft by fimple torrefaction as ftated above, there remains ii'i 

 per cent, for oxygen taken up by the charcoal. 



In this ftate the ore had affiuued a blueifh colour; had 



become bulky and pulverulent, without exhibiting the fmallcft 



fign of malleability : it was, however, fo completely de- 



oxv^enated, and the metal fo much revived, as to deflagrate 



with the rapidity of iron filings, 



I next 



