420 
Cast Steel . 
or cooling that fluid, or from using mercury instead of wa- 
ter ; but it may be remarked, that questions respecting 
the fluid, are, properly speaking, applicable only to files, 
gravers, and such tools as are intended to be left at the j 
extreme of hardness. Yet though Mr. Stodart did not 
seem to attach much value to peculiarities in the process of 
hardening, he mentioned it as the observation and practice 
of one of his workmen, that the charcoal fire should be 
made up with shavings of leather : and upon being asked, 
what good he supposed the leather could do, this workman 
replied, that he could take upon him to say, that he never 
had had a razor crack in the hardening since he had used 
this method, though it was a very common accident be- 
fore. 
One of the greatest difficulties in hardening steel works | 
of any considerable extent, more especially such articles as 
are formed of thin plates, or have a variety of parts of dif- 
ferent sizes, consists in the apparent impracticability of 
heating the thicker parts, before the slighter are burned 
away ; besides which, even for a piece of uniform figure., 
it is no easy matter to make up a fire which shall give a 
speedy heat, and be nearly of the same intensity through- 
out. This difficulty formed a very considerable impedi- 
ment to my success in a course of delicate steel work, in 
which I was engaged about seven years ago ; but after 
various unsuccessful experiments, I succeeded in remov- 
ing it by the use of a bath of melted lead, which for very 
justifiable reasons has been kept a secret till nowx Pure 
lead, that is to say, lead containing little or no tin, is igni- 
ted to a moderate redness, and then well stirred* Into 
this the piece is plunged for a few seconds ; that is to 
say, until when brought near the surface that part does 
not appear less luminous than the rest. The piece is 
then speedily stirred about in the bath, suddenly drawn 
out and plunged into a large mass of water. In this man- 
