THE yOUNG SCIENTIST. 
135 
cabbage-leaf, and the water to roll off the duck's 
back without wetting it. By a somewhat similar 
power, spiders and other insects walk on the 
surface of water without wetting themselves, 
and without sinking in the liquid to any per- 
ceptible degree. 
We have sometimes seen the following solu- 
tion of this problem offered : Fill a plate with 
water to the depth of about a quarter of an 
inch ; a coin is then placed in the water ; a piece 
of paper is lighted, and put, while burning, on 
the surface of the water, and covered with a 
tumbler. As the paper burns under the tum- 
bler, the water will rush up under the tumbler, 
and leave the coin in the plate, when it may be 
lifted without wetting the fingers. This is a 
very interesting experiment, as it affords a good 
illustration of the expansive power of heat, and 
of the pressure of the atmosphere. But when 
we remove the water by atmospheric pressure, 
it is after all merely a scientific way of pouring 
the water out of the plate. 
Price of Rare Metals.— Dr. Theodore Schuc- 
hardt, of Goerlitz, Germany, prepares some of the 
rarer metals, and charges for them the following 
prices : cerium, 20 shillings per gram ; lanthanum, 
40s.; didymium, 30s. These are in globules ob- 
tained by electrolysis. Thorium, in powder, is 
36s. per gram. 
Black Stain for Copper.— Deep black is thus 
obtained upon cleansed copper : Dissolve 3 or 4 oz. 
of blue ashes, hydrocarbonate of copper, in a 
sufficient quantity of aqua ammonia ; place the 
cleansed copper in this solution ; cold or tepid, it 
will be instantaneously covered with a fine black 
deposit. This coat is so thin that burnished arti- 
cles look like varnished black. 
To Varnish Oak.— First rub well with sand- 
paper the length way of the wood, then take about 
2 oz. of raw sienna, l oz. of vandyke brown (in 
water-color), mix with some beer both colors to 
the thickness of ink (if too dark, let down with 
more beer), and apply with a painter's sash tool 
brush, softening off while wet with a larger clean 
brush of any kind, the lengthway of the wood. 
The colors can be obtained at any respectable 
painter's shop. When dry give it a thin coat of 
oak varnish, and do so again after a few days 
have elapsed. 
Emery Belts and Wheels.— Most users of 
emery belts and emery wheels do not use glue 
that is thick enough, fearing it may chill before 
the sand or emery can be spread. In making an 
emery wheel or belt, if the cloth has never been 
glued, it should be sized with glue about as thick 
as lard oil, and allowed to dry thoroughly before 
applying the glue which holds the emery. Have 
the emery heated to 200° Fah.. and coat the belt 
or wheel with glue about as thick as molasses and 
roll it in the hot emery. If a wheel or belt thus 
treated is allowed sufficient time to become 
thoroughly dry it will be very serviceable. 
To Preserve Orchids.— The Gardener's Chron- 
icle states that M. Thuret, the celebrated French 
naturalist, has found a saturated solution of com- 
mon salt to preserve orchid flowers in excellent 
order, even for as long as sixteen years, and to 
answer much better than spirits of wine. This- 
fact cannot be too widely made known to persons 
dwelling in foreign countries, who might thus^ 
send home specimens of new medicinal or other 
plants for description. The editor of that journal 
recommends the use of flat bottles, and the care- 
ful arrangement of the specimens, so that it may 
be possible to examine them without opening the 
bottle. 
To Improve the Appearance of Furniture. 
Take a soft sponge, wet with clean cold water, 
and wash over the article. Then take a soft 
chamois skin, and wipe it clean. Dry the skin as 
well as you can by wringing it in the hands, and 
wipe the water off the furniture, being careful to 
wipe only one way. Never use a dry chamois on 
varnish work. If the varnish is defaced and shows 
white marks, take linseed oil and turpentine, in 
equal parts ; shake them well in a vial, and apply a 
very small quantity on a soft rag until the color is 
restored ; then with a clean soft rag wipe the mix- 
ture off- In deeply carved work the dust can not, 
be removed with a sponge. Use a stiff-haired 
paint-brush instead of a sponge. 
Preparation of a Durable Paste.— Max Ee- 
gensberg recommends the following method for 
preventing mucilage, starch-paste, glue or gelatin 
solutions from spoiling. Any of the above-men- 
tioned solutions or pastes, which should have 
been prepared with hot rain or distilled water, are 
mixed with a few drops of ordinary commercial 
silicate of sodium (silicate of soda) two to three 
drops for every fluid ounce. The preservative 
having been added, the mixture is well stirred 
with a wooden spatula. A solution which has 
already commenced to decompose may be re- 
stored by heating it strongly and adding four to 
flve drops of silicate of sodium for every fluid 
ounce. 
Cutting- Caoutchouc— Dip the knife or cork- 
borer in a solution of caustic potash or soda ; this, 
although the strength matters little, should not 
be weaker than the ordinary reagent solution. 
Water is used in preference to alcohol, which 
evaporates too speedily. When a tolerably sharp 
knife is moistened with soda lye, it goes through 
India rubber as readily as through cork ; the same 
may be said of any cork-borer. By this method 
inch holes may be bored in large caoutchouc stop- 
pers, perfectly smooth and cylindrical. To insure 
a perfect finish to the hole, and no contraction of 
its diameter, the stopper should be firmly pressed 
against the flat surface of common cork till the 
borer passes into the latter. 
