Ox hardening, and tempering Sicel.” 93 
"f was led to thefe reflections by reading Mr. Collier’s 
paper on iron and feel (inferted in the firft number of your 
excellent magazine), in which he gives fome methods of 
hardening and tempering fteel; and concludes by faying, 
that the fprings for penknives are covered over with oil be- 
‘fore they are expofed ‘to the fire to be tempered, but gives 
no reafon for that application. I fhall therefore ath semen 
to fupply that defe&, and add fome other obfervations on. 
the management of fieel, conceiving that any ufeful hint 
on a fubject, fo univerfally applicable to the manufactories 
of ‘this country ‘wilf be of general benefit, Tt is fubje& 
of the firft importance to the practical mechanic: take this 
ufeful fabftance away, and he would be utterly incapable of 
proceeding one f{tep forward, and would foon be convinced 
that ftecl is of more value than gold itfelf. 
For ordinary purpofes, the method noticed by Mr. Collier 
will anfwer very well, both for hardening and tempering; 
but i many cafes it is neceffary that the fteel fhould be of 
the beft quality, and be both hardened and tempered in fuch 
a manner as to preferve the greateft hardnefs poffible without 
brittlenefs ; and fteel is of more or lefs value in propértion 
as it poffeffes this property in a greater or lefs degree. 
Steel, when foft, can be wrought into almoft any form as 
well as iron, welding excepted, of which the better forts, 
particularly caft fteel, are incapable. It can be forged, filed, 
turned in a lathe, drawn into wire, rolled into large plates, 
&e. &¢. and, when by thefe means brought into the defired 
form, it can then be made fo hard as to be capable of cutting 
the hardeft fub{tances (the precious flones excepted), while at 
the fame time it is almoft proof againtt being itfelf worn by 
friction : but in this ftate itis brittle, like all other hard fub- 
flances, and for many purpofes muft have this brittlenefs 
leflened, and this is what is. termed by, workmen, tempering, 
and confifts in giving it certain, degrees of heat according/to 
the temper, defired, whieh may be produced in any degree 
until the whole effeét of hardening is deftroyed, and the'fteel 
is 
