HARDENING OF STEEL. 33 



arrangement, more favourable to the instantaueous expulsion, 



of a larger proportion of caloric. 



To prove this I made experiments with three cylindrical pieces Experiments. 



of steel, six inches long, and half an inch diameter, accurately ste ei'^|° 



turned : the first of which I hardened in the usual way, and on heated and 



examination, found it had deviated from a straight line '05 In. sud ^ en, y 



' a cooled, warp- 



The second piece, I heated just sufficient to occasion a fainted: another 



hissing noise when dipped in the water : then a second time a P lcce repeated- 

 ,. , , , f , . . . . 'y heated and 



little hotter, and quenched it as belore : repeating this operation cooled at suc- 



four or five times, increasing the degree of heat each time ; CC831v e!y ^in- 

 keeping, however, below the hardening point till the last, where did not. 

 it was heated to a blood red and hardened ; and to my surprise 

 remained as perfectly straight and unaltered, as before the 

 operation. 



The third piece I treated in the same way, and experienced A third, piece 

 nearly similar results ; and since the time of making these ex- HkethTse- 

 periments, I have had various opportunities of practising the cond, and with 

 process j and in every instance have found it effectual beyond * hesame re ~ 

 my expectation. 



For smaller articles, to which the above method is not appli- Small articles 

 cable, I have found that by using water whose temperature is were hardened 

 raised to 200°, the steel is not only perfectly hardened, but 

 preserved from the disagreeable consequence, which the use of 

 water at its common temperature, in general produces. 



In the hope that the results of these experiments may prove- 

 useful, I offer them for publicity through the medium of your 

 valuable journal $ from which I readily acknowledge to have 

 derived many hints myself, which have proved important in 

 practice as well as theory. 



E. LYDIATT. 



London, Dec. 5 th, 1812. 



Annotation. W. N. 



As the hardening of steel is higher, and the contraction byAnotherme- 

 cooling, less, the greater the heat of the ignition. I many years f ho< ? b y heaN 

 ago, endeavoured to equalize the heat by igniting in a bath of iefd? ^^ 

 red hot lead, (SeePhilos. Journal, quarto, No. 129.) which lhave 

 constantly found to answer. This method is particularly appli- 



Vol XXXIV— No. 15(5. D cable 



