14 RISE AND PKOGRfcSS 



trading the greatest possible quantity of metal from a given quan. 

 tity of the same kind of ore, has, perhaps, in no one instance 

 ascertained with sufficient precision. There are many sorts of iron 

 and copper ores, which cannot be converted into malleabl metals, 

 without much labour, and a great expense of fuel; it i> v-ry pro- 

 bable, that by a well-conducted series of experiments, more mm. 

 pendious wajs of working these minerals might be found out. Id 

 our own times three new metallic substances hare been disro. 

 vi- red *, and their properties abundantly ascertained by expert* 

 ment; and it may reasonably be conjectured, that future experience 

 will yet augment their number. Till Marggraaf shewed the m -inner 

 of doing it, no metallic substance could be extracted from calamine, 

 and all Europe was supplied with zinct either from India or from 

 Germany. A manufactory of this metallic substance has not many 

 years ago been established in our own country, and the copper 

 works near Bristol hare supplied Birmingham with zinc extracted 

 from calamine. Black-jack was not long since employed in Waleg 

 for mending the roads ; its value is not yet generally known in 

 Derbyshire ; but it is now well understood by some individuals to 

 answer the purpose of calamine for the making of brass J. Mous. 

 Von Swab, in 1738, was, I believe, the first person who distilled 

 zinc from black-jack ; and a work which he erected, probably 

 gave the hint to the establishes of our English manufactory : in- 

 deed, I have been well informed, that they purchased the secret 

 from him when he was in England. The various kinds of black 

 lead, from which neither tin nor iron can at present be procured to 

 advantage ; the mundicks, some cobalt ores, caw k, kebble, and 

 other mineral substances, which are now thought to be useless, may 

 some or time other, perhaps, be applied to good purpose. Cawk 

 and kebble, which are found iu great quantities in mining coun. 

 tries, especially in Derbyshire, and which are universally thrown 

 away, may, perhaps, be nothing but different kinds of spar, and 



* Plat ina, rcgulus of cobalt, and nickel. 



f Zinc is a metallic sub-,tancr of the colour of lead ; when unit<d with cop- 

 per, it constitute* brass, pinchbeck, and other metallic mixtures resembling 



gold. 



J The cobalt ores in Heise, which at present produce a nett profit of about 

 14,0001. a-vear, were formerly u-ed for the name purpose as black-jack was 

 lately in Wales. Bern's Travels by Kaspe, Pre. f i. 



^ Cronitedl'i Miner, lie. *31. 



