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greater weight they are subjected to, the denser and better 
;hey are : for this purpose they are usually cast with a 
neck of half their weight of superfluous iron, which is af- 
terward cut off, having served as a superincumbent weight 
to the roller itself, for the purpose of condensing it. They 
{are then turned in a lathe. My friend Mr. P. who was for 
two years a manager at Mr. John Wilkinson’s iron works 
at Broseley in Shropshire, told me that the experiment of 
{substituting rollers for tilt hammers in the manufacture of 
bars for nail rods, was made at Broseley somewhere about 
the year 1790 ; and that the same power that produced 
72 ton of nail rods per week by means of hammers, pro- 
1 1 300 ton when applied to rollers. 
eable iron thus produced, has the following pro- 
it is a metal of a bluish white colour : it is capable of 
a brilliant polish : it has a styptic taste, when applied to 
the tongue : it has a perceptible odour when rubbed : its 
specific gravity varies from 7, 6. to 7, 8, the specific gra- 
vity of cast iron being about 7, 2 : its specific gravity, 
its tenacity, and its fibrous texture, are increased by cold 
{hammering, rather than by hammering while hot : it is 
{ magnetic : I do not know that any other metal is equally 
so, (steel excepted,) although symptoms of this property 
j have been observed in nickel, and by Mr. Cavallo in 
brass. It has been suspected that this magnetic appear- 
ance has been owing to some small portion of iron being 
mixed as an impurity with the metals in question ; ah 
' though the experiments of Bergman and Thenard seem 
clearly to endow nickel with this property : when iron is 
well made, and hammered both hot and cold to a proper 
point (which may be exceeded) a wire of of an inch 
in diameter will sustain a weight of 549 l~4lb it may be 
fused, according to Sir Geo, Mackenzie, at 158° of 
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