Observations on Lead Ore$. 177 



That of PouLLAEN in Brittany thirty-nine ounces. 



Lead ore is dressed, washed, stamped, and roasted in a 

 reverberatory. 



In Derbyshire a ton of ore is put at once into the furnace. 



Two thousand one hundred pounds of ore do not yield 

 more than one thousand four bundled pounds of lead, or 

 sixty-six per cent. 



Three tons or six thousand pounds of ore are worked 

 off at a smelting house every twenty-four hours. 



Lead ore melted by a wood fire, yields one-tenth more 

 lead than by pit-coal. (Watson IIL 253.) 



The cupola furnace is in general use for the smelting of 

 lead ores in Derbyshire ; (See Watson, IIL 275,) it is a 

 reverbaratory ; this furnace may be constructed any where, 

 and is not noxious to the workmen. 



One ton is put in at a time, and three charges worked off 

 in twenty-four hours ; in six hours from the charging of the 

 furnace the ore becomes fluid as milk ; a bushel of lime is 

 thrown in to absorb the slag, which is then raked to one 

 side ; a hole, previously stopped with clay is opened, and 

 the reduced metal runs out. 



By fusing the lead ore too soon, and raising the heat too 

 high, much of the lead is volatilized, along with the sulphur. 



Derbyshire lead is said to contain two grains of silver in 

 a pound of lead. 



Mine Est Kyr-Kyr, is asserted by some, to afford sixty 

 pounds of silver in every ton of lead ore; by others only four. 



There are some lead ores in Great Britain, which, al= 

 though poor in lead, contain between three and four hun- 

 dred ounces of silver in a ton. 



The best kind of Derbyshire lead ore is worth £7 a ton. 

 (Wat. III. 310.) 



Steel grained lead ore is asserted to be much richer in 

 silver than other kinds." 



There is no place in Derbyshire where silver is now ex- 

 tracted from lead. 



It was done at Matlock a few years since, but is now 

 abandoned, from the faikire of the lead ore ; — it yielded 

 fourteen ounces to a ton. 



* See the remarks on this subject; pa. 69, of the present Number. 



VoL.in....No. L 23 



