USES OP QUICKSILVER, &c. 317 



tions some quicksilver mines in America, near Potosi *, which, he 

 says, God Almighty provided to supply the loss of this mineral, 

 which is very considerable in extracting the silver from the earths 

 and stones with which it is mixed : but the mines of Almaden in 

 Spain are the richest, and probably have been wrought for the 

 longest time of any in the world. Pliny speaks of the cinnabar 

 which the Romans, with so much jealousy, annually fetched from 

 Spain, and it is very probable that they had it from Almaden. M. 

 Jussieu informs us f, that in 1717 there remained above 1200 tons 

 of quicksilver in the magazines at Almaden, after a great deal had 

 been sent to Seville in order to be exported to Peru, where the 

 quicksilver, which is lost in extracting the silver, is said to be at 

 least equal in weight to the silver which is extracted. From 1574, 

 when they began to register the quicksilver, which came to Potosi 

 upon the king of Spain's account, to the year 1640, there had 

 been received, according to Alonso Barba, 204,600 quintals, be- 

 sides a vast quantity irregularly brought in upon other accounts. 

 This application of quicksilver to the extraction of gold and silver 

 from the earths in which they are found, has rendered the con. 

 sumption of it far more considerable since the discovery of the 

 American mines, than it was amongst the ancients. Hoffman 

 forms a calculation, and concludes, that fifty times as much gold 

 as quicksilver was annually extracted from the bowels of the earth : 

 Cramer j admits the truth of this calculation, but insinuates a 

 suspicion worth attending to that mercury may often exist in mi. 

 nerals, and yet not be discovered by miners ; since in the open fires 

 in which minerals, whose properties are not known, are usually 

 examined, the mercury would fly off in fume. Earths or mine, 

 rals of any kind, containing mercury, are most accurately assayed 

 by distilling them with iron filings ; but whether a mineral con- 

 tains mercury or not, may be easily discovered, by strewing it 

 when powdered, on a plate of hot iron, or on a hot brick covered 

 with iron filings, and inverting over it a glass of any kind ; the 

 mercury, if the mineral contains any, will ascend, and attach it. 

 elf in small globules to the side of the glass. Mercury is divided, 

 by the writers of systems of mineralogy, into native mercury, and 

 mercury mineralized by sulphur : native mercury is found in its 



Treatise on Metals, &c. by Alonso Barba. Eog. Trans, p. 118. 



f Hist, de 1'Acftd, dei Scieu. 1719. * Ars Docim. Cram. Vol. I. 9. 131- 



