308 ANNUAL OF SCIENTIFIC DISCOVEEY. 



duty of all the engines at present at work is 51,620,000, while the average 

 duty of the best engines amounts to 99,000,000. This enormous power, 

 which may be estimated at equal to the power of 5,500 horses, is employed to 

 raise more than 9,000 gallons of water per minute from the mines, and to lift 

 a large portion of the ore which is raised. The manufacture of these engines 

 gives rise to other and important industries, each of these large engines cost- 

 ing from 2,000 to 4,000. The machinery at one of the largest mines in 

 Cornwall has been estimated to be of the value of 75,000. From estimates 

 which have been carefully made it appears that nearly 30,000 persons were 

 employed in and about the Cornish mines; of these 5,500 were women, and 

 5,000 children, the women and children being employed on the surface only. 

 In one way or another at least 100,000 persons derive their means of subsist- 

 ence from the tin and copper mines of western England. 



The production of lead from the English mines, for 1853, was 85,121 tons 

 of ore, or 61,021 tons of lead. Most of this lead contains silver which is now 

 profitably extracted. The average produce of silver from the lead ores of 

 Devonshire is 40 ozs. to the ton, those of Cornwall 35 ozs., those of the Isle 

 of Man 20 ozs., of Wales about 15 ozs., of Ireland 10 ozs., and of the northern 

 counties about 6 or 7 ozs. Formerly it was not profitable, by the processes 

 adopted the oxydatiou of lead to separate the silver when it existed in less 

 proportions than 15 ozs. to the ton. By the process of desilveration intro- 

 duced by Mr. Pattinson, it is now economical to separate the silver when not 

 more than 5 ozs. exist in a ton of lead. From this process an enormous 

 amount of wealth has been added to the national store, and there is now 

 obtained from British lead ores at least 700,000 ozs. of silver, which may be 

 valued at 92,500. A process has lately been introduced in which zinc is 

 employed in combination with the fused metal : by the action of affinity the 

 silver is thus readily separated, but as yet this process is not extensively 

 employed. 



Zinc mining receives but little attention in England, nearly the whole sup- 

 ply of the British Islands being derived from Belgium. 



In the working of manganese the English are not able to compete with the 

 German mines. 



The clays of Great Britain are in the highest degree valuable ; the amount 

 raised in 1853 being upward of 100.000 tons. 



During the year 1853 the whole number of iron furnaces in blast was 550, 

 and the total product nearly reached 3,000,000 tons. 



The exact quantity of coal raised is not accurately known ; many of the 

 proprietors of mines declining to furnish information. Mr. Hunt estimates the 

 amount for the year 1853, at about 60,000,000 tons, having a value at the mouth 

 of the pit of 11,000,000, and at the place of consumption of 18.000,000. In 

 producing this quantity 233,650 workmen were employed under ground, and 

 about 50,000 on the surface. Mr. Hunt estimates the quantity of coal remain- 

 ing in the great English coal-fields of Northumberland and Durham, to be 

 equal to 1,251,232,504 Newcastle chaldrons of 53 cwts. each. By this esti- 

 mate, at the present rate of demand, these coal-fields will be exhausted in 331 

 years. 



