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accounted for. It appears to take place more readily in 
scrap iron than in other kinds, and especially if there are 
many fillets or collars, or other inequalities, these appearing 
to destroy the uniformity of the vibrations, and so assist 
in inducing a re-arrangement of the molecules. If a shaft 
or bar be swaged or turned at the end, either larger or 
smaller than the other part of the bar, and it be struck 
at the opposite end with a hammer, the probability is that 
the former part will fly off after a very few blows have been 
struck, unless it be held in the hand, or unless the increase 
or decrease be very gradual. 
By plunging iron when red hot frequently into water, the 
fibres will also lose their form and become quite crystalline, 
and as brittle as cast iron. 
If two pieces of wrought iron work together without 
lubrication, a kind of union takes place between some of 
the particles, and the surfaces of the two pieces are torn 
and galled in a surprising manner. This is termed by 
mechanics " seizing," and is a source of great annoyance 
to them, as it will sometimes happen while fitting portions 
of machinery together. Mr. Samuel Poole, a young 
engineer in our employ, told me that he had seen a cross 
head seized on the end of a piston rod, so that it was 
utterly impossible to move it, except by a hydraulic or 
some very powerful process. 
It is remarkable that most red short irons are tough when 
cold. This is the peculiar quality of the Welsh irons in 
general, but there are some both red short and cold short. 
The best South Staffordshire irons are neither cold short 
nor red short. 
The defect of red shortness is generally attributed to the 
presence of sulphur, cold shortness, to phosphorus, and 
difficulty in welding, to arsenic. I have some reason to 
believe that the addition of flue cinder in the puddling 
