THE YOUNG SCIENTIST. 
47 
wounds being very severe and deep, and that he 
has treated them first with a paste of chalk and 
water, and afterwards with a mixture of chalk 
and olive oil. The latter mixture allayed the 
pain and suffering considerably, and materially 
hastened the healing process, the face-wounds 
being now healed over, forming a perfectly 
healthy skin, 
Paper for Silver-Ware.— The Arcldv der 
Pharmacie gives the following formula for 
making paper for wrapping up silver: Six parts 
of caustic soda are dissolved in water until the 
hydrometer marks 20° Baume. To the solution 
add four parts of oxide of zinc, and boil until it is 
dissolved. Add sufficient water to bring the so- 
lution down to 10° Baume. Paper or calico soaked 
in the solution and dried will effectually preserve 
the most highly-polished silver articles from the 
tarnishing action of the sulphuretted hydrogen 
which is contained in such notable quantities in 
the atmosphere of all large towns. 
Cleaning- Lime-Encrusted Pipes.— A corre- 
spondent of the American Manufacturer writes; 
"As a sort of ' shop kink ' I give you a curious ex- 
periment tried on an engine water-supply pipe 
that had become choked up with lime encrusta- 
tion. After hammering it for an hour or two, and 
kindling a fire all over it, without any result, one 
end was plugged up, and about a pint of refined 
coal oil was poured in the other— all it would 
hold— leaving it to stand all night. The next 
morning the entire mass slid out, a solid lime 
core. Before trying this we thought of throwing 
the pipe away as useless, and getting a new one." 
Blacking* Brass.— A correspondent of the Eyig- 
lish Mechanic says: I have tried all the various 
recipes recommended— nitrate of silver, plati- 
num bichloride, etc.— but never found any work 
so satisfactorily and cheaply done as by the re- 
duction of nitrate of copper to the oxide. I find 
the best way of using is to apply the solution to 
,the brass to be blacked with a camel-hair brush, 
previously slightly heating the metal ; then to 
raise the heat until the requisite color is pro- 
duced; finishing by rubbing with a soft rag, and 
either oiling or lacquering. I can confidently 
recommend this as the very best method of pro- 
ducing that good black seen in first-class optical 
goods, observing that the process will not do for 
soft-soldered articles, as the heat necessary to 
produce the black is greater than the melting- 
point of soft solder. 
Damascus Steel.— Perhaps one of the best 
methods which have ever been discovered for 
tempering steel, resulting in hardness, tough- 
ness, and elasticity combined, is that followed in 
hardening the blades of the famous Damascus 
swords. The furnace in which the blades were 
heated was constructed with a horizontal slit by 
which a current of cold air from the outside 
entered. This slit was always placed on the 
north side of the furnace, and was provided on 
the outside with a flat funnel-shaped attachment 
by which the wind was concentrated and con- 
ducted into the slit. The operation of tempering 
the blades was only performed on those days of 
winter when a cold strong north wind prevailed. 
The sword-blade when bright red hot was lifted 
out of the fire and kept in front of this slit and by 
this means was gradually cooled in the draft of 
air. It acquired the proper degree of temper at 
the single operation. 
QUESTIONS AND ANSWERS. 
How can I bronze plaster casts ? A. B. C. 
Ans— The plaster must first be rendered non- 
absorbent by filling the pores with size. When 
this is dry, give a very light coat of gold size or 
boiled linseed oil, and when this has become 
nearly dry, but is still sticky, dust bronze powder 
over it. When the whole is thoroughly dry, dust 
off the loose powder with a brush, especially from 
the crevices and projecting points. 
i 
Will some one tell me how to make a stereo- 
type of a line of type ? 
Ans.—Lioek up the line of type, as if for print- 
ing, and oil the surface with any kind of oil, 
which must, however, be carefully wiped off, 
merely leaving the surface greasy. Pour over it 
a cream of plaster-of-Paris and water, such as is 
used for taking casts, and when this has become 
hard, lift it off and dry it at a temperature not 
higher than that of boiling water. Make another 
plaster cast with a perfectly smooth face, dry it 
also, and tie the two together. See that the plas- 
ter moulds are quite dry, or you will have trou- 
ble. Make a sprue or channel like that through 
which the lead is poured into a bullet mould, but 
much longer, so as to give a good '"head" of 
metal. This will force the metal into all the fine 
lines and keep it free from air bubbles. Then 
melt some stereotype metal (old stereotypes are 
best for amateurs) in a ladle and pour it into the 
mould. When cold, dress up the easting and 
fasten it on a block. 
Angle-Wobms and St. Elmo's Fire.— You will 
confer a favor on us by answering the following 
questions: "How do angle-worms dig their 
holes ? " and " What is the St. Elmo Fire ? " 
P.S,— We do not know what angle-worms are. 
Several species of worms are known as 
"Angle-Worms," but the term is generally ap- 
plied to the common earth worm. They can 
hardly be said to " dig" holes, but the means by 
which they penetrate the ground is singularly 
interesting. Between the particles of earth they 
insert the very fine end of their lip, which they 
are able to draw out to a very long and slender 
thread. This is armed with spines, so that it can- 
not be drawn back, except at the will of the ani- 
mal. As soon as the front part of the animal has 
been fairly embedded it is made to swell up and 
enlarge the hole sideways, and the mucus or 
slime given off by the animal, cements the side's 
of the hole and makes it smooth. In soft ground 
this process is repeated rapidly, but where the 
soil is very hard the operation is a slow one. 
Still, it is only a question of time even in the 
hardest ground. 
St. Elmo's fire is the silent discharge of electri- 
city from the clouds upon an elevated point. It 
appears as a luminous brush upon masts and 
spires, especially where these are furnished witti 
metal points, such as weather vanes, etc. 
