THE YOUNG 
' varnish for Stained Woods.-A solution of 
■ )ur ounces of sandarac, one ounce gum mastic, 
ad four ounces shellac, in one pound of alcohol, 
) which two ounces oil of turpentine is added, 
an be recommended as a varnish over stained 
'oods. 
Cement for Wood and Iron.— A cement 
lade of oxide of lead and concentrated glycer- 
le, unites wood to iron with remarkable ef- 
ciency. The composition is insoluble in acids, 
5 unaffected by the action of moderate heat, sets 
apidly, and acquires an extraordinary hardness. 
M. Camille Flarumarion, the well-known 
French meteorologist, having been led to believe 
hat the moon contains inhabitants, is making an 
iffort to procure funds to enable him to construct 
i refracting telescope sufficiently powerful to 
how them. The amount which he estimates as 
lecessary is $200,000. 
Black Varnish for Cast Iron.— For those 
)bjects to which it is applicable, one of the best 
!)lack varnishes is obtained by applying boiled 
inseed oil to the iron, the latter being heated to 
I temperature that will just char or blacken the 
)il. The oil seems to enter into the pores of the 
ron, and after such an application the metal re- 
iists rust and corrosive agents very perfectly.— 
imateur's Handbook. 
Imitation Rosewood.— Boil one-half pound 
)f logwood in three pints of water till it is of a 
k^ery dark red ; add one-half ounce of salt of tar- 
:ar. Stain the work with the liquor while it is 
1 boiling hot, giving three coats; then, with a 
painter's graining brush, form streaks with the 
following liquor: Boil one-half pound of logwood 
chips in two quarts of water; add one ounce 
pearlash, and apply hot. 
Cement for Steam Joints.— Take sal-am- 
moniac, two ounces: sublimed sulphur, one 
ounce ; fine cast iron turnings, one pound ; mix 
in a mortar, and keep dry. When to be used, mix 
; with twenty times its quantity of clean iron turn- 
ings or filings, and triturate the whole in a mor- 
tar; then wet with water until of proper consist- 
9nce. A red putty for steam joints can be made 
of stiff white lead worked well in red lead 
powder. 
The latest experiments with guns of the 
largest size are quite interesting. The highest 
velocity imparted to the shot is 1,626 feet per 
second. This is equal to a mile in a very little 
more than three seconds (3.2 seconds). The 
i pressure on the interior of the gun was 19)^ tons. 
In previous experiments, however, where a less 
velocity was obtained, the pressure was 21 tons. 
The increased velocity is attributed to the greater 
size of the grains of powder used, and it is laid 
down as an axiom that the larger the gun the 
larger must be the grains of powder. 
Varnish for Basket Ware.— The following 
varnish for basket work is said to dry rapidly, to 
possess sufficient elasticity, and to be applicable 
with or without admixture of color: Heat 375 
SCIENTIST. 47 
grains of good linseed oil on a sand bath until it 
becomes stringy, and a drop placed on a c^ld, 
inclined surface does not run ; then add gradually 
7,500 grains of copal oil varnish, or any other 
copal varnish. As considerable effervescence 
takes place, a large vessel is necessary. The de- 
sired consistency is given to it, when cold, by ad- 
dition of oil of turpentine. 
To Make Corks Air-tight and Water-tight. 
—A German chemical journal commends the use 
of parafflne as the best method of making porous 
corks gas-tight and water-tight. Allow the corks 
to remain for about five minutes beneath the sur- 
face of melted parafflne in a suitable vessel, the 
corks being held down either by a perforated lid, 
wire screen, or similar device. Corks thus pre- 
pared can be easily cut and bored, have a per- 
fectly smooth exterior, may be introduced and 
removed from the neck of a flask with ease, and 
make a perfect seal. 
Black Varnish for Optical Work.— The 
external surfaces of brass and iron are generally 
blacked or bronzed with compositions called 
lacquers. The insides of the tubes of telescopes 
and microscopes should be coated with a dead 
black varnish so as to absorb the light and pre- 
vent any glare. The varnish that is generally 
used for this purpose consists of lampblack made 
liquid by means of a very thin solution of shellac 
in alcohol, but such varnish, even when laid on 
warm metal, is very apt to scale off, and thus pro- 
duce two serious evils— the exposure of the bright 
metallic surface, and the deposit of specks on the 
lenses. It will therefore be found that lamp- 
black, carefully ground in turpentine, to which 
about a fifth of its volume of gold size or boiled 
linseed oil has been added, will adhere much 
more firmly. The metal should be warm when 
the varnish is applied.— J.maiewr's Handbook. 
Stretching" Tracing Paper.— The thin, trans- 
parent tracing paper, used by architects and 
draughtsmen, can be stretched or be mounted so 
as to give a fine even surface, on which water- 
coloring and shading can be done as easily as 
upon mounted paper. Cut a piece of drawing- 
paper the size of the drawing-board; gum the 
upper surface edge of the board, about half an 
inch in width ; spread the tracing paper carefully 
over the drawing, and smooth down on the 
gummed edge ; then turn the sheet back, and 
gum the remaining three edges of the board; 
bring over the tracing paper, and smooth down 
the edges ; do not pull or twist the sheet, so as to 
get it tight or severely strained, but get the edges 
well held down by the gum. After the gum has 
dried, a clean sponge, well saturated with water, 
may be passed over the entire surface, except on 
the gummed edges. The tracing-paper expands 
and blisters all over, but in a few minutes the 
dampness evaporates, and a beautiful surface is 
presented, similar to a transparent slate. The 
tracing can now be colored or shaded as on draw- 
ing paper, and any blots or errors can easily be 
washed out. 
