286 



METALS. 



very moderate firing, and lasts two hours ; the second fire for smelting 

 requiring a higher heat with shut doors, and at the end the slags are 

 dried up with lime, and the furnace is also allowed to cool a little ; the 

 third and fourth fires, also for smelting, requiring a still higher tem- 

 perature. 



A furnace for using the hot blast with lead has been contrived. The 

 heated blast is made to diffuse itself equally through the whole " charge," 

 carrying with it the flame of the burning fuel, and the reduction of the 

 ore is effected with an economy and dispatch hitherto unknown in the 

 processes of reducing this metal.* 



According to another mode which has been practised in Germany and 

 France, old iron (about 28 per cent.) is thrown into the melted ore, 

 heated in a reverberatory furnace of small size ; the iron acts by ab- 

 sorbing the sulphur, and the lead thus reduced flows into the bottom 

 of the basin. There is here a gain of time and labor, but a total loss 

 of the iron. 



The mode of obtaining the silver from lead ore, is mentioned under 

 Silver. 



The principal mines of lead in the world are mentioned under Galena, 

 The following is a statement of the approximate amount of lead pro- 

 duced by the mines of Europe : 



Great Britain and 



Ireland, . . 1,200,000 cwt. 

 Spain, .... 600,000 " 

 Austria, . . . 140,000 " 

 Russia and Poland, 6,000 " 

 France, .... 30,000 " 



Sweden and Norway, 4,000 cwt. 

 Prussia, . . . 160,000 " 



Germany, . 160,000 " 



Belgium, . . . 20,000 " 

 Piedmont and Switz- 

 erland, .... 10,000 " 



According to the Statistical Tables of J. D. Whitney ,t the mines of 

 the Upper Mississippi and Missouri have afforded as follows : 



Upper Mississippi. Missouri Mines. 



1826, ... 428 tons. . . . 1,343 tons. 



1,832 

 3,227 

 2,793 

 3,348 



1,500 1 



The present yield of the Missouri mines is set down as not over 1500 

 tons. The proceeds of the western mines have been for many years 

 on the decrease. 



1830, 



5,331 



1835, . 



. 8,469 



1840, 



11,987 



1842, . 



. 13,992 



1845, 



24,328 



1847, . 



. 24,145 



1850, 



17,768 



1853, . 



. 13,307 



What other method is mentioned 1 What country affords the largest 

 amount of lead at the present time, and how much ? What is the yield 

 of the mines of the Upper Mississippi. What of the Lower or Mis- 

 eouri mines 1 



* See Amer. Jour. Sci. xlii, p. 169. 



t Whitney's Metallic Wealth of the United St 



ites, p. 421. 



