With respect to steel, in 1831 the process in use was that of
cementation, producing blistered steel, which was either piled and
welded to make shear steel, or was broken into small pieces, melted in
pots, and run into an ingot weighing only some 50 lb. or 60 lb. At
that time steel was dealt in by the pound; nobody thought of steel in
tons. In 1881, we are all aware that, by Sir Henry Bessemer's
well-known discovery, carried out by him with such persistent vigor,
cast iron is, by the blowing process, converted into steel, and that
of Dr. Siemens' equally well-known process (now that, owing to his
invention of the regenerative furnace, it is possible to obtain the
necessary high temperature), steel is made upon the open hearth. We
are, moreover, aware that, by both of these processes, steel is
produced in quantities of many tons at a single operation, with the
result that as instanced in the case of the North-Eastern rails, steel
is a cheaper material than the wrought iron made by the puddling
process. One cannot pass away from the steel manufacture without
alluding to Sir Joseph Whitworth's process of putting a pressure on
the steel while in a tried state. By this means, the cavities which
are frequently to be found in the ingot of a large size are, while the
steel is fluid, rendered considerably smaller, and the steel is
thereby rendered much more sound. In conclusion of my observations on
the subject of iron and steel manufacture, I wish to call attention to
the invention of Messrs. Thomas & Gilchrist, by which ores of iron,
containing impurities that unfitted them to be used in the manufacture
of steel, are now freed from these impurities, and are thus brought
into use for steel-making purposes.

BRIDGES.

In the year 1831, bridges of cast iron existed; but no attempt had
been made to employ wrought iron in girder bridges, although Telford
had employed it in the Menai Suspension Bridge; but in 1881, the
introduction of railways, and the improvement in iron manufactures,
have demanded, and have rendered possible the execution of such
bridges as the tubular one, spanning the Menai Straits, in span of 400
feet, and the Saltash, over the Tamar, with spans of 435 feet; while
recent great improvements in the manufacture of steel have rendered
possible the contemplated construction of the Forth Bridge, where
there are to be spans of 1,700 feet, or one-third of a mile in length.
Mr. Barlow, one of the engineers of this b