he men of bronze suddenly
invaded and extirpated the men of flint; and that at some still later
period, another stronger and more skilful race, supposed to have been
Celts from Gaul, came armed with iron weapons, to whom the men of
bronze succumbed, or with whom, more probably, they gradually
intermingled. When iron, or rather steel, came into use, its
superiority in affording a cutting edge was so decisive that it seems
to have supplanted bronze almost at once;[4] the latter metal
continuing to be employed only for the purpose of making scabbards or
sword-handles. Shortly after the commencement of the iron age, the
lake-habitations were abandoned, the only settlement of this later
epoch yet discovered being that at Tene, on Lake Neufchatel: and it is
a remarkable circumstance, showing the great antiquity of the
lake-dwellings, that they are not mentioned by any of the Roman
historians.

That iron should have been one of the last of the metals to come into
general use, is partly accounted for by the circumstance that iron,
though one of the most generally diffused of minerals, never presents
itself in a natural state, except in meteorites; and that to recognise
its ores, and then to separate the metal from its matrix, demands the
exercise of no small amount of observation and invention. Persons
unacquainted with minerals would be unable to discover the slightest
affinity between the rough ironstone as brought up from the mine, and
the iron or steel of commerce. To unpractised eyes they would seem to
possess no properties in common, and it is only after subjecting the
stone to severe processes of manufacture that usable metal can be
obtained from it. The effectual reduction of the ore requires an
intense heat, maintained by artificial methods, such as furnaces and
blowing apparatus.[5] But it is principally in combination with other
elements that iron is so valuable when compared with other metals.
Thus, when combined with carbon, in varying proportions, substances are
produced, so different, but each so valuable, that they might almost be
regarded in the light of distinct metals,--such, for example, as
cast-iron, and cast and bar steel; the various qualities of iron
enabling it to be used for purposes so opposite as a steel pen and a
railroad, the needle of a mariner's compass and an Armstrong gun, a
surgeon's lancet and a steam engine, the mainspring of a watch and an
iron ship, a pair of scissors and a Nasmyth