434 
Cast Steel, 
situation above described, must, though still fluid, have 
been cooled down to the temperature of the surrounding 
snow, which was still found to be 22 \ Upon taking 
them out, I found the pieces hard but brittle, having the 
appearance of steel that had been overheated. 
Being disappointed in what I had expected, I in- 
tended to repeat the experiment with a still lower heat ; 
but an alteration in the state of the air prevented me 
from prosecuting the experiment at that time, and having 
since succeeded in making use of quicksilver instead of I 
water, I have never resumed the experiment. As me-, 
thods are now well known by which water may be cooled I! 
below the freezing point, even by the fire side, and at am 
easy expense, some one who has, time may perhaps think 
the experiment worth repeating : it might cast some light I 
upon the subject of hardening steel, and lead to some 
useful results 
The dish I employ for tempering is made of plate-iron, 
with an edge turned up on every side a sufficient height 
to hold tallow or oil enough to cover the pieces to be tem- 
pered, The corners are nipped together, and then i 
folded up against the sides ; by which means they are 
prevented from letting out the oil. 
Another turned up on three sides only, is used to lay 
pieces intended to be hardened : a cover is of advantage 
where the pieces are intended to come out clean and bright, 
as it more perfectly defends them from the air, and of 
course prevents oxidation from taking place. By this 
instrument, the work, though ever so small or slender, 
may be brought out of the fire and dropped into the wa- 
ter with very little loss of heat. It ought to be made of 
stronger plate- iron than is necessary for the other pan, 
and the corners cut out so that the sides may bend up 
more square. They need not be folded as in the otl^er, not 
