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The ironstones of the oolites, as at present known, may be 
sub-divided into — 
1st. Those of the Middlesborough and Yorkshire fields. 
2nd. Those of the Midland Districts. 
The first, containing from 30 to 33 per cent, of iron, of a 
cold short character, but admirably adapted for foundry 
purposes, from the sound character of the castings which 
they make. 
The second vary very much in character, and in the per 
centage of iron which they contain, varying from 20 to 55 
per cent. They generally contain but a small proportion of 
alumina. The proportion of silica varies very much ; some- 
times rising as high as 40 to 50 per cent., while some 
varieties contain only 2 or 3 per cent. Carbonate of lime 
is occasionally largely present. These ores are said, by 
those who have most largely tested them, to produce iron 
of fair quality ; but as they are only recently beginning to 
be used, some time will elapse before they are thoroughly 
understood. From the large beds in which they occur, 
sometimes 12 to 25 feet thick, they must ultimately exercise 
considerable influence on the iron trade. 
The other known classes of ore are not of sufficient 
importance to require any enumeration here. 
Although bar iron is very commonly divided by persons 
unacquainted with its varieties into two great classes, namely, 
good iron and bad iron, yet these terms can only be correctly 
interpreted to mean that a certain iron is suitable or un- 
suitable for the purpose to which it is applied; for I am 
not aware that there is any iron manufactured to be equally 
suitable for all purposes, nor that there is any so worthless 
as to be suitable for none. Some iron may be tough 
and able to bear great longitudinal strain : such iron is 
DO ' 
particularly fit for chains and chain cables, but unless 
it will weld easily without requiring such a heat as to 
