The Middlebury register and Addison County journal. [volume] (Middlebury, Vt.) 1883-1885, 1884-04-18
A LOST ART REDISCOVERED.
THE ANCIENTS' BLACK MIRRORS
MADE FROM FURNACE STAG.
n Visit to Pompcii Results i'm Exc
pcriments which Way Revolution.
izc the Making OF Glassware.


tiers of glass manufacture in the United
States, and any new discovery relating
to it is always of interest here. Obsid-
ian, it may be prcmised is u species of
volcanic glass, and one of the lost arts
was the manufacture of various articles
from this material, among them black
mirrors, which are used in the making of
optical astronomical instruments. In
the twelfth and thirteenth centuries mir
rors were made from an obsldian stone,
and used principally by the Peruvians
The first mirror for optical astronomical
purposes was made from obsidian in the
year 1879, by Franciscan monk johann
nus Pcckham who called it Perspective
Communis. He gave the first satisGac-
tory prescription for the manufacture of
mirrors from this material. That they had
been known at an earlier day is shown by
their mention in Plinys writings. In the
course of time the secret of their manu-
facture was lost In the earliest ages
mirrors were made from polished metal.
Glass mirrors ovcraid with silver were
used in Europe to some extent in the
thirteenth century, Venice being the seat
of their manufacture. From Venice the
art went to Bohemia, at that time called
"the mother of glass manufacture. and
it was not until 1865 that it was con-
vcyed to France by one Colbert,
chemist
Mr.. Enrico Rosonzi, of this city, who
is entitled to the honor of having rcdis-
covered the lost art, is a native OF Italy,
a chemist by profession and practice,
having studied in one OF the leading
German universities He is now citi-
zen of Pittsburg, and here conducted
the experiment which ended in his final
success His attention was first directed
to the subject in 1879, while on visit to
Pompeii. Here he found fragment of
a statue-an arm-made from obsidian,
and its evident kinship to the lava there
so abundant led him to think it might
have been made therefrom Bringing
away with him his trophy and quantity
of lava, he began an investigation and
series of experiments which finally
led him to a knowledge not only
of the component elements of obsidian,
but also as how it might be reproduced
by artificial means. Like all investiwa-
tors he met with many obstacles and dis
couragements, all of VIII CHI only served
to make him pcrsevcre more energctically.
His first experiments looking toward the
reproduction of the material were made
at a Pittsburg glass house and Others in
the furnaces of several Of our local steel
works. His first successful melt was
made at the glass factory of George Dun
can e Sons. in the latter part Of 1891.
He there made a number of ornamental
articles and several slabs of the new
glass, and later went to New York city
and set up small furnace for its man
ufacturc He one day visited the best
known manufacturer of optical lenses
in the United States, Mr.. Wcskopf, and
asked what he would charge for polish
ing a slab Of it, which he laid before the
great man. Mr. WciskOpf wantel to
know what it was, and when he got the
information curly named high price
for polishing it. Much to his astonish-
ment Mr.. Rosenzi accepted his terms and
a day was named when the work was to
be completed When he called for it
Mr.. Rosenzi was surprised to find all
of Mr., Weiskopf's brusquerie gone.
"Do you know what you have
done2" the latter inquired. You have
rcdiscovered the lost art of making black
mirrors. Don't get excited and think
there's millions in it for you, because
but few of them are used, yet your dis
covery is of the greatest scientific i'm
portance." When it came to receiving
/ pay for his work he smiled and said
"No, | want no money. Just bring me
| a slab like this, or even smaller and
will be well paid" He got the slab and
| from it made mirror which is now IN
/ his possession in New York city. The
first one he made for Mr. Resent is
now in st. Petersburg, whittier it was
sent by the consul-genera( of that coun-
try to whom Mr. Resent presented it..
The new material ha, been patented
under the name of "ferroline." OF
course the articles entering into its com
position are the secret of the discoverer,
1 but the basic material is furnace Stag.
1t melts at 1900 degrees to 1900 de
grees F., and can be worked in eighteen
to twenty hours after the materials are
placed in the melting pot. Its quail
tiles are great hardness and strength
far superior to glass, capablity OF
being either cast like molten iron OF
blown or pressed like glass, and suscepti-
bility to the highest possible polish. 1t
is opaque, the thinnest sheet of it sue
cessfully resisting the passage of light; is
not attacked b. any kind Of acid, and
has clean, highly-polished fracture.
Commercially it is we'll adapted for the
manufacture of tops for tables and
bureaus, slabs or plates for inlaying fur
niturc mlrble or wood mantels, for
opaque bottles for druggists, fruit jar:
and for wall and other ornaments. Ii
will take the place of glass in many use:
for which the latter is poorly ad lpted
Its cost is some greater than glass, bal
not sufficiently so to render its use TO
the above purpose too costly. Mr., Ro
SEMI has not yet entered upon its manu-
facture except on an experimental scale
but expects to do SO at no distant day
There are millions upon millions OF tons
Of furnace Stag in this country which cal
be converted by this process from Il posi-
tive incumbrance to Il useful purpose