fna78s dan 
XIL. A Pofffeript to Mr. Vanuey’s Paper on the Methods 
of hardening and tempering Steel. 
Oni looking over the paper I ion for the laft. Number of 
the Philofophical Magazine (fee p. 92), I fee that I omitted 
mentioning an experiment or two conneéed with the fub- 
ject, which I meant to have introduced into it. 
As fteel is always found more compact and ftrong bodied 
when hardened with a low heat, and as that effeét is beft, 
obtained the colder the water is which is employed in hard- 
ening it, provided the water is clean, a circumftance which 
fhould always be attended to, it appeared probable, that if 
water was cooled down to the freezing point, or even lower, 
which it may be, and retain its fluidity, by being kept in @ 
ftate of perfect reft, the effect might be heightened. I 
caufed a large heap of fnow to be colleéted together at a 
time when the thermometer ftood at 22° of Fahrenheit, and 
making a deep hollow in the middie, I fet a glafs of clean 
water in the bottom of the hollow, and covered the whole 
with a board to prevent the air from difturbing or caufing 
any motion in the water. I heated fome pieces of fteel in 
the breech end of a gun barrel to a low red heat; and by 
means of an affiftant to take off the board at the inftant L 
arrived with the heated barrel and its contents, I quickly 
dropped the pieces into the water; which haying ftood all 
the preceding night in the fituation above defcribed, muft, 
though ftill fluid, have been cooled down to the tempe- 
rature of the furrounding fnow, which was ftill found to be 
22°. Upon taking them out; I found the pieces hard but 
brittle, having the appearance of fieel that had: been over- 
heated. 
Being difappointed in what I had cura I intended to 
repeat the experiment with a {till lower heat; but an altera- 
tion in the {tate of the air prevented, me from profecuting: 
the experiment at that time, and having fince fucceeded in- 
making 
