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cast iron had a power about one-third greater than the power 

 of the inferior. But he tried it another way. Having found 

 that the accumulating magnetic capabilities of substances, 

 in relation to their number, became another test of quality, 

 he began to try them one upon another, taking the exact 

 quantity the compass diverged after each addition. He put 

 a second of the best quality, and found that the divergence 

 of the compass was about 18 deg., while No. 3 was only 12 

 deg. 30 min. Six plates of the best cast iron thus combined 

 produced a deviation of 25 deg. 47 min., while the inferior 

 only produced a deviation of 17 deg. 44 min., being 8 deg. 

 less than the deviations of the best series. He did not mean 

 to say that the theory was established on which this principle 

 of testing cast iron was founded : it would require many more 

 experiments : but yet so far as his experiments had gone, the 

 object he had in view was fully realized, for it had been shown 

 that they could detect quality by a scientific mode without 

 breaking into metal — they could discern the diff*erent qualities 

 in the kinds he had compared to a nicety, equal to that which 

 would be shown by weighing 15s. in gold and a sovereign. 

 He next proceeded to the application of the principle to the 

 determining of the quality of steel. He believed that there 

 were really no scientific means established besides that which 

 he had suggested, of determining the quality of steel gene- 

 rally. The methods in use consisted in the exercise of that 

 sort of knowledge which arose from constant mechanical 

 practice and observation; and the best judges of steel by 

 these means were the men who worked on it. They esti- 

 mated something of the quality by the appearance when 

 broken; but they were not unfrequently deceived by the 

 fracture. By this appearance they might suppose that a piece 

 of steel was as good as possible — a beautiful quality — and yet 

 when they come to work it into cutlery it perhaps would not 

 do. Thus the working well and tempering well, with the 



