MECHANICS AND USEFUL ARTS. 49 



THE STEEL MANUFACTURES OF SHEFFIELD, ENGLAND. 



THE London Patent Journal furnishes the following statistics relative 

 to the steel manufacture of Sheffield : 



Judging from the state of trade, the production of steel in Sheffield, 

 in 1850, could not have been less than 23,000, probably 25,000 tons, 

 though the average produce of the last five years would probably not 

 exceed 17,500 to 19,000 tons. WQ have no means of ascertaining 

 the quantity of steel used in the home manufactures, but, judging from 

 the annexed statement of the exports of steel, \ve feel convinced 

 that we are not far short of the mark hi the above calculation. The 

 following table shows the progress of the steel trade, at quinquennial 

 periods, during the last thirty years ; the second column showing the 

 quantity exported, and the third column the export to the United 

 States, which is our principal market. 



Years. Tons. Tons. 



1820, 326 ... .85 



1825, .... 533 .. 130 



1830, .... 832 397 



1835, .... 2,810 .... 1,886 



1840, .... 2,583 . . . 1,202 



1844, .... 5,121 .... 2,376 



1849, .... 8,085 .... 5,216 



The quantity exported in 1850 was 10,587 tons, of the declared 

 value of 393,659. 



COMPARATIVE ELASTICITY OF WROUGHT AND CAST IRON". 



THE mean ultimate resistance of wrought-iron to a force of compres- 

 sion, as useful in practice, is 12 tons per square inch, while the crush- 

 ing weight of cast-iron is 49 tons per square inch ; but for a considerable 

 range under equal weights, the cast-iron is twice as elastic or compresses 

 twice as much as the wrought-iron. A remarkable illustration of the 

 effect of intense strain on cast-iron was witnessed by the author at the 

 works of Messrs. Easton & Amos. The subject of the experiment was a 

 cast-iron cylinder, 10| inches thick, and 14 inches high, the external 

 diameter being 18 inches. It was requisite for a specific purpose to 

 reduce the internal diameter to 3 inches, and this \vas effected by the 

 insertion of a smaller cast-iron cylinder into the centre of the large one ; 

 and to insure some initial strain, the large cylinder was expanded by 

 heating it, and the internal cylinder, being first turned too large, was 

 thus powerfully compressed. The inner cylinder was partly filled with 

 pewter, and, a steel piston being fitted to the bore, a pressure of 972 

 tons was put on the steel piston. The steel was upset by the pressure, 

 and the internal diameter of the small cylinder was increased by full 

 three sixteenths of an inch ; that is, the diameter became 3-f-ths of an 

 inch. A new piston was accordingly adapted to these dimensions ; and 

 in this state the cylinder continues to be used and to resist the pres- 

 sure. The external layer of the inner cylinder was thus permanently 

 extended 8-Vrths of its length. In fact, it can only be regarded as loose 

 packing, giving no additional strength to the cylinder. Under these 



5 



