Vast Steel 
435 
being intended to hold any liquid substance. Such ar- 
ticles as small drills, pendulum and other small springs, 
need not be dropped into water, but only made to pass 
j through the air by tossing them out and letting them fall 
to the ground, which will make them hard enough for 
most purposes. 
Small drills may be hardened by holding their points 
in the flame of a candle, and, when sufficiently hot, sud- 
denly plucking them out : the air will harden them ; and 
i they may then be tempered, by taking a little of the tal- 
low upon their point, and then passing them through the 
I flame at about half an inch above the point, and holding 
| them there till the tallow begins to smoke. This method, 
known to all watchmakers, may be of use to other artists, 
and therefore not unworthy of the notice I have taken 
of it, S. Varley. 2 Phil. Mag. 
Properties of blued Steel not generally known, 
IN making springs of steel the metal is drawn or ham- 
mered out and fashioned to the desired figure. It is then 
hardened by ignition to a low red heat and plunging it in 
water, which renders it quite brittle. And lastly, it is tem- 
pered either by blazing or bluing. The operation of blaz- 
ing, consists in smearing the article with oil or fat, and then 
heating it till thick vapours are emitted and burn off with 
a blaze. I suppose this temperature to be nearly the same 
as that of boiling mercury, which is generally reckoned 
to be at the 600 of Fahrenheit, though for reasons I shall 
in future mention, I think this point requires to be exam- 
ined. The operation of bluing consists in first bright- 
ening the surface of the steel, and then exposing it to 
the regulated heat of a plate of metal or a charcoal fire, 
or the flame of a lamp until the surface acquires a blue 
colour by oxidation. The remarkable facts which I have 
heie to present to the notice of philosophers, are, that Mr, 
