Cast Steel. 
locks, various articles in clock and watcli work, <kc. &c. 
The necessity of making them bright enough to mark the 
change of colour is obviated by smearing them with oil 
or tallow, which helps to apply the heat more uniformly, 
and marks the temper as well as by observing the colour, or 
nearly so ; or by putting the things to be tempered into a 
proper vessel, and adding so much oil or tallow as will 
cover them, and then holding them over the fire or the 
flame of a lamp until a sufficient heat is given. By this 
means the most irregular pieces may be uniformly heated, 
and great numbers may be done at one time, and with 
great certainty : thus are clock and watch pinions, watch 
verges, balances, &x, tempered ; sometimes many do- 
zens at once ; and no more time is necessary for the whole 
than would be for one single article. The requisite tem- 
per may be known by the following circumstances : 
When such a heat is given that the tallow is first observed 
to smoke, it indicates the same temper as that called a 
straw colour : this will reduce the hardness but little ; 
but if the heat is continued until the smoke becomes 
more abundant, and of a darker colour, it will be equal 
to a brown, and indicates a temper that may be wrought — - 
that is, which may be turned or filed, but with difficulty, 
and only when a mild sort of steel is employed. If the 
tallow be heated so as to yield a black smoke, and still 
more abundant, this will denote a purple temper ; and if 
the steel is good, it will now work more pleasantly, 
though still hard enough to wear well in machinery. The 
next degree may be known by the tallow taking fire if a 
lighted body is presented to it, but yet not so hot as 
to continue to bum when the light is withdrawn ; this 
would equal a full blue colour. Increase the heat till the 
tallow continue to burn, being once lighted, and this will 
denote a pale blue : and if the whole of the tallow be al- 
lowed to burn away, or to bum dry, as the workmen call 
