MECHANICS AND USEFUL ARTS. 65 



f Leather belt on iron pulley slipped at 48 Ibs. 

 " " * leather " " " 6-1 Ibs. 

 " " rubber " " 153 Ibs. 



The next experiment was with vulcanized rubber. A three-ply belt of 

 the same diameter, length, and thickness as the leather one, was chosen, 

 and being loaded with thirty-two pounds to keep it " taut/' weights were 

 added, as in the former instance, and the result was as follows : 



Rubber belt on iron pulley slipped at 90 Ibs. 

 " " " leather" " 128 Ibs. 



" " " rubber" " 183 Ibs. 



MINIXG ENTERPRISE. 



The deepest coalpit in Great Britain, and probably in the world, has, after 

 nearly twelve years' labor, during which some important mining problems 

 have been solved, been completed, and opened at Dunkinficld, Cheshire, 

 England. The shaft of this extraordinary pit is G8G1 yards deep, and the 

 sinking of it has cost nearly 100,000. The undertaking was commenced in 

 1817, by Mr. Francis Astley, who is lord of the manor of Dunkinfield, a 

 township of 1203 acres in extent, and containing valuable beds of coal. By 

 September 1818, the shaft of the pit had been sunk 220 yards, when the 

 works were stopped by the tapping of a copious spring of water, which ren- 

 dered it necessary to put in pumps and drive a tunnel 80 yards long. In 

 about fourteen months this work was completed, and 43 yards added to the 

 depth of the pit. Shortly afterwards another spring was encountered, which 

 stopped the works three months. At the end of five years from the com- 

 mencement, a depth of 470 yards had been attained, the last 103 yards hav- 

 ing occupied twenty-nine months, in consequence of the difficulties which 

 had to be overcome, the rock pierced through being very hard, and another 

 tunnel 400 yards long having had to be made. At this point the sinking of 

 the shaft was suspended for a time, and the mine was worked for coal ; but 

 in 1857 it was determined to sink the shaft to the Black-mine, a further 

 depth of 21G? yards. Operations proceeded steadily, in the face of many 

 difficulties and discouraging predictions; but the enterprise was recently 

 successfully completed by the workmen winning the Black-mine, a fine scam 

 of coal 4 ft. 8} in. thick, and calculated to last thirty years at 500 tons per 

 day. In sinking the shaft, twenty-two workable seams of coal were passed 

 through, as well as eight other seams, varying from 1 to feet thick, and in 

 the aggregate 10-3 feet in thickness. The shaft is generally 12 ft. G in. in di- 

 ameter, but near the bottom it expands to a diameter of 19 ft. 2 in. It is 

 lined with bricks 9 inches thick, with strong rings of stone at intervals of 

 8 yards. At the bottom of the shaft is an incline nearly half a mile long. 

 The pit is fitted with very powerful machinery. Another shaft of the same 

 depth is sunk as an air draught. London Times. 



ON THE INFLUENCE OF CHEMICAL MANUFACTORIES ON ANIMAL 



AND VEGETABLE HEALTH. 



A recent inquiry on the above subject, instituted by the Belgian govern- 

 ment, merits attention. For some years, a notion had grown into a belief 

 that certain manufactories were prejudicial to health and vegetation; and so, 

 much disquiet arose thereupon, especially in the province of Namur, that 



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