Hisro.Rr of the sociETr. 31 



place; and had the filver been here, in the loweft degree of in- 

 candefcence, or the hlgheft degree of obfcure heat, the pheno^ 

 menon would have been as remarkable as in the fulphuratlng 

 of metals. 



On the fame principle it feems to be, that, in a very common, 

 but very inftrudive experiment, a bar of cold iron is made in- 

 candefcent, by hammering it with a certain degree of rapidity 

 and force, fo that the condenfation may be fufficiently quick to 

 expel the heat all at the fame time, or nearly fo. In this cafe. 

 It is tlie latent heat of dudility that is made to appear, as in the 

 congelation of water it is the latent heat of fluidity. 



Iron alfo furnilhes another example of the fame kind, where 

 the mcandefcence is very confpicuous, but where the procefs is 

 not fo fimple as in the former inftances, becaufe a part of the 

 light IS probably produced from another caufe. This example 

 IS found in the converfion of pig iron into malleable iron by 

 Mr Corte's procefs, viz. by keeping the iron melted in a re- 

 verbatory furnace, and expofed,by being agitated, to the influ- 

 ence of the atmo^Dhere. When the caft iron comes in this man- 

 ner to Its malleable ftate, it quickly difplays the brighteft incan- 

 defcence poflible, coagulating, at the fame time, from its melted 

 ftate. Now, there can be no doubt that this extreme incandef- 

 cence anfes from the commutation of latent into fenfible heat 

 and the commutation of that heat again into light, in which 

 Itate it is emitted by the incandefcent body. In this cafe, how- 

 ever it is probable, that there is alfo, light emitted immediately 

 on the principle of burning, and that the iron is in part fcori- 

 fied, by being oxygenated and lofing its phlogifton. But this 

 alfo IS m a great meafure owing to the extreme heat produced 

 by the congelation of the iron; for the heat of melted iron is 

 not alone fufficient for that effed. 



The theory above laid down will enable us to explain all 

 the difi^erent fteps in the complicated procefs of the fulphurating 



of 



