270 Mr. Stodart and Mr. Faraday on the alloys of steel. 
and this is more particularly to be attended to when the al- 
loying metal is fusible at a low temperature, as silver. The 
same care is to be observed in hardening : the article is 
to be brought to a cherry-red colour, and then instantly 
quenched in the cold fluid. 
In tempering, which is best performed in a metallic bath 
properly constructed, the bath will require to be heated for 
the respective alloys, from about 70° to ioo° of Fahrenheit 
above the point of temperature required for the best cast 
steel. We would farther recommend, that this act of tem- 
pering be performed twice ; that is, at the usual time before 
grinding, and again just before the last polish is given to the 
blade. This second tempering may perhaps appear super- 
fluous, but upon trial its utility will be readily admitted. We 
were led to adopt the practice by analogy, when considering 
the process of making and tempering watch springs. 
