THE YOUNG SCIENTIST. 
81 
soap left in the leather that allows the 
finer particles of tiie leather to separate 
and become soft like silk. After rinsing, 
wring it well in a rough towel and dry 
quickly, then pull it about and brush it 
well, and it will become softer and better 
than most new leathers. In using a rough 
leather to touch up highly polished sur- 
faces, it is freqently observed to scratch 
the work ; this is caused by particles of 
dust, and even hard rouge, that are left 
in the leather, and if removed by a clean 
rougey brush it will then give the bright- 
est and best finish, which all good work- 
men like to see on their work. 
Ebonizing Wood. 
ALL the world now knows of those arti- 
cles of furniture of a beautiful dead- 
black color, with sharj:), clear-cut edges, 
and a smooth surface, the wood of which 
seems to have the density of ebony. 
Viewing them side by side with furniture 
rendered black by paint and varnish, the 
difference is so sensible that the consider- 
able margin of price separating the two 
kinds explains itself without need of any 
commentary. The operations are much 
longer and much more minute in this 
mode of charcoal polishing, which re- 
spects every detail of the carving, while 
paint and varnish would clog up the holes 
and widen the ridges. In the first process 
they employ only carefully selected woods, 
of a close and compact grain ; they cover 
them with a coat of logwood dissolved in 
water, and almost immediately after- 
wards with another coat, composed chiefly 
of sulphate and acetate of iron. The two 
compositions, in blending, penetrate the 
wood, and give it an indelible tinge, and, 
at the same time, render it impervious to 
the attacks of insects. 
When these two coats are sufficiently 
dry, they rub the surface of the wood at 
first with a very hard brush of couch- 
grass (cMendent), and then with charcoal 
of substances as light and friable as pos- 
sible, because if a single hard grain re- 
mained in the charcoal, this alone would 
scratch the surface, which they wish, on 
the contrary, to render perfectly smooth. 
The flat parts are rubbed with natural 
stick charcoal, the indented portions and 
crevices with charcoal powder. At once, 
almost simultaneously, and alternately 
with the charcoal, the workmen also rubs 
his piece of furniture with flannel soaked 
m linseed oil and the essence of turi)en- 
tine. These pouncings, repeated several 
times, cause the charcoal powder and the 
oil to penetrate into the wood, giving 
the article of furniture a beautiful color 
and perfect polish, which has none of the 
flaws of ordinary varnish. Black wood, 
polished with charcoal, is coming day by 
day to be in greater demand ; it is most 
serviceable ; it does not tarnish like gild- 
ing, nor grow yellow like white wood, and 
in furnishing a drawing-room, it agrees 
very happily with gilt bronzes and rich 
stuiTs. In the dining-room, too, it is 
thoroughly in its place to show off the 
plate to the greatest advantage, and in 
the library it supplies a capital frame- 
work for handsomely bound books.— 
Cabinet Make7\ 
Mosaics. 
THE extraordinary delicacy and accu- 
racy acquired by workers in Mosaic, 
both as regards shape and color, form a 
marked illustration of the power of physi- 
cal education. In a portrait of Pope Pius 
V. there were, 1,700,000 pieces each no 
larger than a grain of millet. The 
enamel is a kind of glass colored with 
metallic oxides, which is fused and drawn 
out into threads, small rods, or oblong 
sticks of varying degrees of fineness, 
slightly resembling the type used by com- 
positors. These many colored rods are 
kept in drawers properly numbered, so 
that the artist always knows to which 
case to repair when he requires a fresh 
supply of a particular tint or tints. When 
the picture is commenced the first step 
is to place on the easel a slab of marble, 
copper, or slate, of the sized fixed upon ; 
and this slab is hollowed out to a depth 
of about three and a half inches, leaving 
a flat border all round which will be on a 
level with the completed mosaic. The 
excavated slab is intersected by trans- 
verse grooves or channels so as to hold 
more tenaciously the cement in which the 
mounts of enamel will be embedded. 
Then the hollowed slab is filled with 
" gesso," or plaster-of- Paris, on which the 
proposed design is accurately traced in 
outline, and usually in pen and ink. 
The artist then proceeds to scoop out a 
small portion of the plaster with a little 
sharp tool. He fills up the cavity thus 
made with wet cement or '•'mastic," and 
into this mastic he successively thrusts 
the " spiculae," or the " tesserae, " as the 
case may be, according to the pattern at 
his side. In the broad folds of drapery or 
in the even shadows of a background, or 
a clear sky, his morsels of enamel may 
be as large as one of a pair of dice ; in 
the details of lips, or eyes, or hair, or 
foliage, or flowers, the bits of glass may be 
no larger than pins' heads. The cement, 
or mastic, is made in various ways, the 
best being formed of slaked lime, finely 
powdered Tiburtine marble, and linseed 
oil, and when thoroughly dry is as hard 
as flint. Sometimes the mastic which 
Alls the cavity is smoothed and painted 
in fresco with an exact replica of the pat- 
