368 PHILOSOPHICAL TRANSACTIONS, [aNNO 1753. 



prove, that the iron is not converted into copper ; since, according to Sir Isaac 

 Newton's table, the specific gravity of copper is to that of iron as 9000 to 

 7645. 



When he was at this spring in August last, it ran at the rate of 12 oz. every 

 second ; and by putting iron into the water of the stream running from the pits, 

 he found, that every ounce contained 3 grs. of copper. Hence by calculation it 

 appears, that 129600 grains of copper are carried off every minute, and conse- 

 quently 1241001b. Troy weight in a year; supposing the quantity and quality 

 of the water to continue the same. Hence we may easily account for the death 

 of the fish, and other phenomena in the river, which receives this vitriolic 

 stream. 



In a hot sunny day, when the water is exhaled, the heaps of mould, raised out of the 

 ore-pits, are covered with a vitriolic efflorescence : hence, in rainy weather, the 

 water appears like a strong solution of verdigrise. Whoever is desirous to imitate 

 the process carried on in these pits, may readily gratify his curiosity, by putting 

 pieces of iron into strong solution of vitriol. It is a common experiment, to 

 tinge polished iron by rubbing it with Roman vitriol ; which depends on the 

 cause before-mentioned ; viz. the acid in the vitriol penetrates the iron, and 

 leaves the copper on the surface. This experiment is also taken notice of by 

 that excellent chemist, and celebrated philosopher, Mr. Boyle, who calls it a 

 sympathetic precipitation, in his Essay on specific Medicines. 



As soon as the attraction between the copper and the acid ceases, the mutual 

 attraction between the minute particles of the metal prevails, so as to form large 

 solid masses at the bottom of the pits, -^ of which are pure copper. These so- 

 lid masses are partly occasioned by the pressure of the incumbent heap of granu- 

 lated copper, constantly increasing. Hence we see, that the art of essaying, or 

 separating metals from their ores, chiefly consists in evaporating an acid, which 

 prevents the mutual attraction of the metallic particles : for when the acid is 

 driven off by the violence of fire, the particles fall into their proper sphere of 

 attraction, and assume a solid form. From what has been offered on the theory 

 of this admirable process, several practical hints may be taken to render such 

 springs more profitable ; and perhaps an easier method may be discovered of se- 

 parating copper from its ore, by precipitation, than by calcination. 



This spring perhaps is as remarkable for its medicinal as its metallic qualities. 

 Though physicians generally reckon copper, taken internally, poisonous, yet the 

 miners and other people drink this .water frequently, without any ill conse- 

 quences. It purges and vomits severely, and is become their specific in several 

 diseases, particularly in cutaneous eruptions, arising either from an alkaline 

 acrimony in the blood, which stimulates the sensible extremities of the cuta- 

 neous arteries, and occasions a pustule, or from the irritation of insects lodged 



