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 bridge, has told me that
there will be used upwards of 2,000 more tons of material in the Forth
Bridge, to resist the wind pressure, than would have been needed if no
wind had to be taken into account, and if the question of the simple
weight to be carried had alone to be considered. With respect to the
foundation of bridges, that ingenious man, Lord Cochrane, patented a
mode of sinking foundations, even before the first meeting of the