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district, the ores sometimes attain a thickness of 30 feet, then 
again, the yield of iron in the Bradford district is only from 
30 or 35 per cent. 
The Ironstone of South Yorkshire is also of very good 
quality. It is nodular, and in some places these nodules are 
so numerous as to form a seam, yet it retains its nodular 
character, and these seams are intermittent, extending only 
a few feet and then being absent a few feet more. It is worked 
at three different depths, the Black Shale Mine, about 13 
yards above the Silkstone coal, is got through a depth of 5 
or 6 feet ; the top, or what is called the Brown Mine giving 
the most plentiful supply, being 9 inches thick. In the 
remaining height, the balls are picked out of the shale. All 
the ore in this working added together, would onl}- give a 
solid thickness of about I foot. 
About 62 yards above this ironstone, or 20 yards below 
the Parkgate coals, is the White Mine. 
Twenty-five yards above the Parkgate coal is the Black 
Mine. On account of the great cost of getting these ores, 
they are fast going out of use, their place being supplied 
by others, such as those of Lincolnshire and Barrow, which 
are found in much larger quantities, and are considerably 
cheaper. The South Yorkshire ores are also mixed with, 
and improve the quality of, those above mentioned. 
Iron is found associated with sulphur, phosphorus, 
silicon, and other substances, and occasionally with titanium. 
These substances are all more or less deleterious to the metal, 
for while phosphorus makes it cold-short, that is to say, 
brittle when cold, while it does not affect it when hot, sulphur 
makes it red-short, that is, it causes it to fly to pieces or brittle 
when hammered red-hot, but does not affect it when cold, 
and siKcon renders the iron brittle and weaker in tension. 
There are large quantities of very rich titanic ores in Xorway, 
New Zealand, and other places. These are only used to a 
