om Scotland in this case--and it contains a small
per cent. of copper. We don't care much about it; we seldom have it;
but it is sold at the ticketings regularly. For want of a better name,
we term it _slag_; but it is not slag, properly so called, which you
see all around you. A better denomination is that employed in
designating it in the Journal--namely, _rubbish_.'[5]

'You make no kind of distinction in the ore-yard,' we continued. 'Is
that unnecessary?'

'Well, practically it is. As these heaps lie, you can perceive that a
vertical slice from top to bottom will give us a tolerably even
admixture of the different ores. This is always desirable to a certain
extent, since the ores being of different constitution, the one
materially assists in the reduction of the other. Thus an ore
containing a large proportion of fluor-spar may with great advantage
be employed to flux another containing felspar or quartz, which
substances are almost infusible alone. Indeed, the judicious admixture
of ores constitutes the most important vocation of the smelter; and it
is to this that the copper-houses of Swansea are indebted for one of
their advantages over the proprietors of mines, who, possessing only
one kind of ore--rich, probably, but intractable--can never bring it
into the state of a metal with any satisfactory profit.'

'What is the value of these ores?'

'That varies much. This gray sulphuret contains about 70 per cent. of
copper, and is worth L.35 per ton. This yellow sulphuret, from being
mixed with a large quantity of iron and silicious earth, contains only
about 12 or 14 per cent. Some malachites contain so much as 50 per
cent., and others less pure, 30 to 40 per cent. of copper. But the
greater mass of the ores we melt have a far less produce than this.
That Cornish ore you see there, for example, contains only 4-1/2 per
cent. of metal. The average produce, however, of all the British and
foreign ores smelted at Swansea may be given at about 12 per cent.
Previous to the great increase of foreign importation, it was much
lower.'

We now come to the process of smelting. The theory of reducing
metallic ores, of whatever constitution, is to bring them to the state
of oxides; and then, by the addition of charcoal, and with the aid of
heat, to expel the oxygen in the form of carbonic acid; after which
the pure metal is left. In practice, the reduction of copper-ores is
slightly different. Here the object is to separate,