smelted with charcoal. This
kind of ore is found in several countries, particularly in Spain. In New
Zealand, at New Plymouth it is said to be found in great quantities; but from
the two countries first mentioned we obtain a supply of from 12,000 to 15,000
tons, of which about 9000 come from Sweden. The celebrated mines of Danemora
produce the finest Swedish iron, and only a limited quantity is allowed to be
produced each year. All the steel-iron used in England is imported into
Hull. Bar-steel is manufactured by heating the iron, divided into lumps, in
pots, with layers of charcoal, closely covered over with sand and clay, for
several days. By this means the iron is carbonized and converted into what
is commonly called blistered steel. The heat is kept up a longer or shorter
time according to the hardness required.

Bar-steel, as it comes from the furnace, is divided and sorted, and the
pieces free from flaws and blisters are rolled out and converted into files,
knives, coach-springs, razors, and common implements, according to quality.
It will be seen that there is a good deal of science and judgment required to
manufacture the best steel.

Sheer steel is made from bar-steel by repeated heating, hammering, and
welding.

Cast steel, a very valuable invention, which has in a great degree superseded
sheer steel for many purposes, was first made in 1770 by Mr. Hunstman, at
Allercliff, near Sheffield. It is made by subjecting bar-steel, of a certain
degree of hardness, to an intense heat, for two or three hours, in a
crucible, and then casting it in ingots.

The Indian Wootz steel, of which such fine specimens were exhibited in the
Exhibition, and from which extraordinary sabres have been made, is cast
steel, but, from the rudeness of the process, rarely obtained perfect in any
quantity. Whenever we have the good fortune to intersect India with
railroads, steel-iron will be among the number of our enlarged imports.

The hard and elastic qualities of steel, known as "temper," are obtained by
heating and then cooling rapidly. For this purpose baths of mercury and of
boiling oil are used. Some waters are supposed to have peculiar virtues for
tempering steel.

Case-hardening, a process much used for tools and plough-shares, consists in
superficially hardening cast iron or wrought iron by heating it in a charcoal
crucible, and so converting it into steel.

The successful operations for converting steel into var