GEOLOGY. 307 



Great Britain from Singapore, India, China, Peru, and Brazil, amounts to 

 2,500 tons. Of this foreign tin there is re-exported about 1,000 tons, and of 

 British tin rather more annually. The average production of the five largest 

 tin mines of England for 1853 was about 250 tons, the maximum produce 

 being 282 tons. 



Out of the tin produce arises another, but not very extensive, branch of 

 mineral industry the production of arsenic ; most of the tin ores contain both 

 that substance and sulphur, which are got rid of by exposing the powdered 

 ores in peculiarly constructed furnaces to the action of fire. The quantity of 

 arsenic annually produced has been estimated at 2,000 tons ; the chief market 

 for it is, however, now closed, the principal portion of it having been used in 

 the preparation of Russian leather. 



In 1853 the value of the copper ore sold in Cornwall was 1,155,167 ; and, 

 in addition to this, Ireland produced 11,278 tons of copper ore, and some hun- 

 dreds of tons were produced in "Wales and the northern English counties. The 

 importance of some scientific knowledge to the mining population is well ex- 

 emplified by the fact, that hundreds of tons of the gray sulphuret of copper 

 have been thrown over the cliffs of the western shores into the Atlantic Ocean, 

 and hedges have been built with copper ores of twice the value of the ordin- 

 ary copper pyrites. Immense masses of the black oxyd of copper had from 

 time to time been thrown aside ; eventually, the miner became acquainted 

 with the value of these ores, and they are now, of course, carefully preserved 

 whenever they occur. 



Mr. Hunt gives some details of the produce of the principal copper mines 

 in Cornwall, whence all the copper ore raised is sent to Swansea, the trade 

 employing about 150 vessels and 800 seamen. The ships carry back coal to 

 Cornwall, which is employed chiefly in the production of the mechanical force 

 by which the water is pumped from the mines and the ores raised. The 

 smelting establishments of Swansea support, by their direct or indirect influ- 

 ence, nearly 15,000 people : thus we have an example of the effects of a pe- 

 culiar branch of industry rising up at a distance from the locality in which the 

 material sought for is produced. The importation of copper ores from the 

 mines of Cuba, Chili, etc., would, it was feared, greatly reduce the value of the 

 British ore. Now, although Cuba exports to England 15,000 tons of her rich 

 ore annually, Chili at least 18,000, and Peru, Spain, South Australia, and our 

 other colonies, about 20,000 tons more, the value of the Cornish copper ores 

 have steadily increased, the combination of the two being necessary for the 

 production of the best kinds of metal. 



Mr. Hunt describes the Cornish pumping-engine as, perhaps, the best ex- 

 ample of the application of steam as a motive-power which the world had yet 

 produced. This superiority he attributed to the necessity imposed upon the 

 engineers of effecting a great economy of fuel, in a locality so far distant from 

 the coal-fields; and, again to the circumstance that the duties of the engines 

 were regularly reported in what are called "duty papers." The duty of a 

 Cornish pumping-engine is estimated by the number of pounds lifted a foot 

 high by the consumption of a bushel of coals. Taylor's engine, at the United 

 Mines, reached the high duty of lifting 110,000,000 pounds. The average 



