Burlington free press. [volume] (Burlington, Vt.) 1827-1865, 1843-05-26

out some OF more properly metaurgIcal char
acer deserve notice. One ofthese is the improve.
mcnt by which iron is made capable Of castinr
into the lightest and most delicate objects, pos.
sesslng the thinncss Of sheet iron, and the sharp.
ness and smootlnrss Of castings in bronze or The
finer metals. The process was discovered at
Berlin, and the articles cast in this wav are
known by the name of Berlin iron. la conncx
ION with this, may mention the process invented
by the sculptor Chantry for casting small and
slender objects, such as twigs of trees with all
Their leaves. His mode, emitting some mi.
nor details, was this. The object is suspended in
an empty cylinder, and the finest silt, mixed
with wafer to the consistcnce Of cream, is very
gradually poured in, until the cylinder is filed
and the object covered The whole being nj.
lowed to dry, the object remains imbeddcd in
the silt, and perfect mould is left if the object
can be removed. This is accomplished in the
following way. Before the object is suspended
IN the cylinder, numerous fine wires are slight
ly attached to the extremitics of the principal
leaves or buds. After the mould is drv, these
wires are withdrawn and the mould being ex-
posed to red heat, streams of air are directed to
the holes left by the wire The consequence is
that the branch is consumed, aud all the solid
matter OF which it was composed being carried off,
the mould is left ready to receive the melted me.
tai, which is poured in while the mould is red hot
The only remaining improvements, which
shall mention under tn head, are the discovery
: VI w itiu'lli1 CISt IRON tough ana nal
lcablc which is now extensively employed and
the recent application Of electro rnc,ism TO
metnllurglcal processes. Some of these | shall
notice more particularly. The most extensive
use yet made of this improvement is in gliding
and silvering, which is thus performed The
object to be gilt or plated which must be metal.
lie, or have received metallic surface bv coat.
ing with black lead or some other simple process.
is placed in solution of salt of gold or silver
by means of clectro-magnctsm, the metallic
salt IN solution is made to rc-assume its metallic
form, and is deposited on the surface of the oh.
lect which thus becomes permanently coated
with film or leaf of gold or silver, the thick
ness OF whnh the artist can regulate. This pro-
cess has been seized upon by iasp.coners, and
great quantities of false money gilt or svercd
by this means are in circulation. The false rold
is very difficult of detection, for platinum, from
which the coins are struck, is of so nearly the
same specific gravity as gold that the difference
Is hardly pcrccptiblc, and the false coin can only
be detected by cutting The same art has also
been applied to the multiplication of engraved
plates, ny similar process, with this difference,
That the deposited metal must be of considerable
thickness, and it takes from the engraved
plate cast with lines in relief corresponding TO
the lntaglio OF the plate, the process must be re.
peated, and new cast taken from the first in the
same manner. This is found perfect fac .sme
OF the original engraved plate, and the most
prnctlscd eye cannot distinguish the smallest
difference IN impressions printed from them
The original plate may thus be preserved as
model, from which an unlimited number of per.
iect copies can be taken. Engravings on wood
are multiplied in the same way, the blocks first
receiving metallic surface. This process also
furnishes means of obtaining metals in greater
purity than by any other known mode, for Ger.
tam ACIDS which dissolve gold, silver, or copper
will not take up those metals with which thew are
nlloyed, and thus perfect chemical separation
The mechanical improvements in the WORKING
OF metals are so numerous, that very small
portion OF them can he noticed. The most i'm
portant are those by which metals are shaprd.
either into finished utensils, or into more con ven.
rent forms for subsequent working. The chief
o: these is the rolling mill in all lis varieties
by rolling, iron and other metals are drawn into
bars Hat, square, round, grooved, not only with
economy and dispatch, but with n precision
nnattalnable by the hammer. BY the same
means, metals are reduced to sheets of any de.
srabIe thickness, from the heavy plates for steam
boilers, to the thin sheets employed for timing
Inc RUSSIA sheet iron SO remarkable for its hard
ana polished surface is however produced by
ditfereni and, as is said, secret process and lead
cannot be reduced by rolling to the thinness of
mat with which the chinese tea chests are lined
The chinese method is said to be by pouring
melted lead alloyed with tin a smooth marble
slab and letting similar slab fall upon the met
al as 1t begins to cool The trip. hammer, BY
which heavy anchors and even shafts many feet
IN length and sometimes eighteen inches in d.
alnrter, are forged, is modern, as are the var.
Gus machines for manufacturing nails. spike =
horseshoes pms, screws and other articles oi cut
bent, stamped, or twisted metal Perhaps the
most ingenious and beautiful machines of this
descrp t'on are those employed in coinage -
Most OF the contrlvances employed in the Euro
pean minis are due TO the genius of Watt the
great improvcr of the steam engine. The ma
chimes invented by him were capable of stamp
ing 300 pieces in an hour, a single stroke per-
forming the whole operation The mint at
Philadelphia is admirably conducted, and is the
most interesting mechanical spectacle of which
our country can boast. The art of gold beating
though not perhaps modern invention, is com.
, paratively recent in some of its details, and is
probably carried to greater perfection than il
) was by the ancients. The process is this A
plate of fine gold beaten thin by the hammer, six
! or eight inches in length three fourths of an
inch wide, and weighing about two ounces. is
passed between rollers until reduced to the
thnness of paper, and extended into a ribbon
about ten feet in length, without increase in
, width This is cut into about 80 square pie
ces each of which is separately forged an an
wi, until is about an inch square, and one eight
hnndredh part of an inch in thickness The
, whole 100 squares are now intcraid with pieces
OF fine vellum four inches square, and the pack
, ct is enveloped in parchment and beaten with n
heavy hammer, on marble block, unit. the gold
is extended to nearly the size of the vcllum.-
/ The packet is then opened, and each leaf of
, gold is divided into four. These are n,erlaid
| with pieces of animal membrane called gold
beater's skin, of the same dimensions as the vel
lum. The packet is now beaten until the leaves
are extended as before, after which they
quartered, and the process is again repeated until
the leaves are once more brought to the extent
, of nearly four inches, In this way two ounces
of gold are made to cover a surface of more
than go square feet, and the process may be
continued even beyond this.
OF the numerous new uses Of the metals,
can mention but few An important one is the
construction Of bridges supported by archcd
frame work of cast iron which have been in use
more than half century. Of these bridges the
most celebrated is that of Southwark at London
This the Thames by three arches, the
span of the largest of which is $40 feet, and
there are other iron bridges of nearly equal di-
mcnsons. Iron has been for some time applied
to the construction Of roofs, both the covering
and frame work being sometimes of that metal
and more lately dwelling houses have been built
Of considerable dime nsions with walls of double