accuracy of his electrical theory, Dr. Smith
caused a quantity of slag, fresh from the
smelting-house, to flow upon a non-conducting
substance, where it was allowed to cool much
more gradually than was usually the case.
To his great delight he found that he had
obtained a most complete verification of his
opinion. The product thus obtained had
entirely lost its semi-vitreous and friable
character, and assumed a dense, solid, and
rocky nature, capable of resisting the heaviest
blows, and altogether assuming the
peculiarities of the igneous rocks.

Having obtained this result, the experimenter
proceeded to other trials. By continuing
the molten slag, when removed from
the furnace, at a high temperature, in an
oven, where it was afterwards allowed to
cool very gradually, aud then run into moulds
of a non-conducting substance, the material
was found to have become altogether de-
vitrified, and to have taken a beautifully veined
and granulated character of extreme hardness,
approaching to the solidity and strength
of the finest marble. By varying the heat
applied, by the admixture of colouring matters,
and by a subsequent polish applied to
the surface, the experimenter has succeeded
in producing a perfect imitation of cornelian,
agate, malachite, or any other of the more
valuable mineral products.

Here then we see how an enquiry having
for its object the elucidation of a purely
scientific theory, has led the inquirer, by
imperceptible steps, to a most valuable
discovery, by means of which many million of tons
of hitherto refuse matter may be converted
into really useful and valuable materials
for the builder, the architect, and the
decorator.

Already, in America, the slag of iron furnaces,
in its new character, is employed for
paving purposes with the most complete
success, whole thoroughfares having been, for
several years, laid down with this material,
without any perceptible wear of the surface.
In the form of building-bricks it is likewise
in considerable use; and builders in some of
the principal cities of the United States testify
to the perfect adaptation of such bricks, and
to their great superiority and economy over
the common clay brick.

It is not easy to limit the application of
this valuable. rubbish. Wherever durability
is required, united with peculiarity of form,
there the prepared slag will be found
perfectly adapted; for, inasmuch as it can be
cast into moulds of any shape, all labour
spent in hewing and cutting marble or stone
is avoided. It is perfectly compact and
impervious, and therefore admirably suited
for the construction of aqueducts of any
size. It remains unacted on by chemicals
of the greatest strength, consequently
may be employed for making gas-piping, as
it will last out many of the ordinary iron
pipes.

When wrought in its higher character, run
into suitable moulds, aud polished more
brilliantly than marble or porphyry, it will
furnish pillars, facades, slabs, &c., for the
ornamentation of mansions, halls, and public
buildings, at a price and in a style not
hitherto attained. We have specimens of
this beautifully polished material before us,
and certainly we can see in it that which is
likely to bring about a complete revolution
in house architecture. Who will be content
with porous bricks, perishable stucco-work, or
soft crumbling stone, when such adamantine
cornelian-like material is to be had, that
shall defy the action of London smoke and
factory vapours? We can picture in our
mind's eye a new Belgravia, a second
Tyburnia, rising up at the bidding of some
adventurous Cubitt or Peto, built with slag bricks,
and faced with a polished front of surpassing
brilliancy, in the most exquisite forms,
and apparently composed of marble, agate,
cornelian, porphyry, and malachite. If a
shade of dust or smoke settle on it, the first
shower of rain restores it to its original
brilliancy. Time will have little, if any,
effect on it; and as for repairs or beautifying
every third or fourth year, such care
would never be needed. All this we expect
to see before many seasons shall have passed
over us.

It is impossible to over-estimate the advantages
likely to arise from this new branch of
industry, so simple in its application, yet so
widely available in most European countries,
not only with the refuse products of iron-
works, but with those resulting from the
smelting of copper, lead, and zinc ores. The
rough slabs or tiles for pavements or roofing
can be sold, with a large profit, at fourpence-
halfpenny the foot. When highly polished,
at eighteenpence. In its more finished and
ornamented forms, for architectural purposes,
this material possesses, of course, a much
greater value, dependent on its durability and
beauty.

Regarding this important discovery from
whatsoever point of view, whether in reference
to the vast quantity of now useless
refuse that may be made valuable, to the
many interests that will be benefited by it,
iron-masters, copper-smelters, builders, architects,
house-decorators, and water-companies,
we cannot but look upon it as one of the
most promising results of modern science in
an age peculiarly fruitful in marvellous
inventions, and rich in its daily Penny
Wisdom.

We have, in. a previous paper, shown the
marvellous powers of electricity, in the
production of light. Here we find the same
subtle element busily employed in making
mere rubbish a beautiful and useful adjunct
to the arts. How far the same agency may
be made subservient to the improving of
our smelted metals and other products uf the
furnace, we dare not venture to predict. We