Vermont watchman and State journal. [volume] (Montpelier, Vt.) 1836-1883, 1843-07-21
MISCELLANY.
HISTORY OF THE MECHANIC ARTS.

7ddreSs delivered before Burlington Mechanics In
SHue, By GEO. Z. MARSH, and published 6y
request Of The Institute.
(Conduded)
Under the head of works in glass may be rang
ed mosaic, an art known TO the Greeks aud Ro-
mans, and still very successfully praclised. 1t
originally consisted in joining together small pie.
ces OF marble md other Opaque stone of various
shapes, sizes aud colours IN such way as 10 rep
resent natural and artificial olerts on plane sur
lace, like picture, and was first employ ed in or.
nalnenlai paving. Afterwards The precious stones
were used III the same way, and exquisely beau
liiul works IN these costly materials, requiring an
Incredible amount of Time aud lubour, now
produced at Florence. But the material now gem
orally used IN mosaic is Opaque glass OF different
colours drawn out into slender rods. Short pie
ces OF these rods broken off by the workmen
and arranged III frame, side by side, presenting
the ends 10 the spectator, us to imilaiae paint
ing with great perfection. The joints are SO close
us not 10 he percepble, without close exanin-
aton, and when The surface is ground and polish =
ed, The effect is scarcely Inferior to tina, of The lin
esl works IN oil. This art is OF great value as Il
means OF perpetuatlng those masterpieces which,
from tie decay OF the wood or canvass OH which
they are painted, and the fading and the solIing OF
the coOrs, Gun calculate on duration of but a
lew centuries at most. Works in mosaic may be
made OF any desirable thickness, aud sometimes
pies mus Obtained. The number Of shades OF col
our, used III the mosaic fabric at Rome is $4,000,
anu even these hardly suffice 10 reproduce all The
iinls employed IN painting. Large pictures have
peen copied IN this way, and among Others the
celebrated Last supper Of Da Vinci. The copy
Is OF The same size us The original being thirty
ieel IN length and fifteen in height The figures
are considerably above the size of life, aud the
pieces oil glass of which this mosaic is composed
snow surface oil from one twelfth 10 one fourth
OF an inch square, which is however much above
Inc SIZE oil Tie pieces used in smaller mOsalcs. 1t
occupied The constant labor Of five skillul artists
Ior eight years. aud cost above S32 900.
In the middle ages, stained window glass was
one oil the principal decorations of ecclesiastical
structures aud was carried to an admirable de-
gree OF perfection. This art, after having fallen
hiuch into decay, has been lately revived, aud spe.
clnlens are now produced at Munich, in no wise
inferior 10 the finest from The middle sges.
The principal modern improvements in glass are
in casting large plates for mirrors, afterwards
ground and polished, and in It's adaptation TO OPP
lical purposes, to which The progress of modern
astronomy aud many branches OF physical sci
ence Is IN great measure 10 be Inscribed The
invention OF achromaic object glasses for lee
scopes ny Dolland was an in The art, and the
Ehgllsh mad Tor many years the highest repula.
ion Tor optical Instruments, but The improvements
OF EuInaud IN France, aud Fraunholel aud his
successors III BaVhrn, have led 10 the production
oil large masses OF glass of great TRANSPARENCY,
and perfectly homogeneous aud uniform in tex.
iure, "a point of great difficulty and relracling tel
escapes are now made at Munich of much great.
er power and excellence, Than any hitherto at
tempted in England.
We have no direct evidence that the oncients
possessed any means of aiding the sigh, by omi-
cal instruments or even that they were ACQUAINTED
with the magniiyng power of convex transparent
nlAt I..s IL.
properly should have escaped The notice of their
glass workers, and The use of magnifers by them
has been inferred, with great probability, from the
extreme minuteness aud delicacy OF their wrought