430 
Cast Steeh 
have one end of a bar drawn out into a small rod under a 
low heat, an obscure red for instance, or but little above \ 
then heat it as before, and suddenly plunge it into pure 
cold water : if it proves hard, and requires a great force 
to break it, it is good, let its fracture be what it may : and 
I have always found that the specimens that hardened 
with the lowest heat, and when in that state required the 
greatest force to break them, proved the best steeh Hav- 
ing thus selected steel fit for the required use, and, with 
the precautions already noticed, given it the proper form, 
it may be hardened ; but the same method will not an- 
swer for all purposes. Some pieces, from their size and 
figure, are very difficult to be hardened ; if they are large, 
they heat the water in immediate contact with them, and 
the heat is communicated to the rest of the water, so fast 
that it prevents the pieces from being cooled quick enough 
to produce the desired effect : this is in part prevented by 
continually moving the piece about in the water ; but 
vvh n too large to be hardened by this method, a stream of 
water must be employed ; and for such pieces as the face 
of large anvils, a birch broom is used with advantage to 
break the bubbles that are formed by the continual disen- 
gagement of air, and which, if not swept away, would 
prevent that intimate contact and uniform succession of 
the stream necessary to produce the degree of hardness 
required. Other articles from their length, are difficult, 
and almost impossible to be made hard without bending, 
or otherwise altering their figure : this circumstance oc- 
casions a great deal of trouble ; and many a piece of work 
is spoiled, after a good deal of labour has been bestowed 
upon it. The method that has succeeded best with me 
is, either to inclose the piece or pieces intended to be 
hardened in an iron case or box, open at one end (for the 
more ready dropping the pieces into the w T ater), and giv- 
ing It a slow yet regular heat; then to take the case out 
