THE YOUNG 
SCIENTIST. 
curiosity of all, however, was a copy of the 
Bible, written by one Peter Bales, a chancery 
clerk, in so small a book that it could be in- 
closed within the shell of an English walnut. 
A steam-engine which can be covered by an 
ordinary thimble has been constructed by an 
American watchmaker named Beck. Its height 
is only sixteen millimetres, and the space it oc- 
cupies is less than three square centimetres. 
Its weight is one gramme. It has no fewer than 
140 distinct pieces connected by means of 102 
screws, yet the little machine works perfectly. 
PolisMng Wood-Work. 
Soft woods may be turned so smooth as to re- 
quire no other polish than that which can be 
given by holding fine shavings of the same 
wood against them in the lathe. For polishing 
mahogany, walnut and some other woods, the 
following formula is given : Dissolve beeswax 
by heat in spirits of turpentine until the mix- 
ture becomes viscid. Apply with a clean cloth, 
and rub thoroughly with another piece of cloth. 
Beeswax is sometimes alone used. For work 
in position, it must be melted and applied and 
rubbed as above. For work in the lathe, it can 
be applied by friction, the slight amount of wax 
melted being sufficient for the polish. The 
work should be thoroughly rubbed. Mahogany 
may be polished by rubbing first with linseed 
oil, and then by a cloth dipped in very fine brick 
dust. Some hard woods have a natural polish, 
and do not require a polishing medium. A fine 
gloss can be produced by rubbing with linseed 
oil, and then holding shavings or turnings of 
the same material against the work in the 
lathe. A very perfect surface can be obtained 
with glass paper, which, if followed by hard 
rubbing, will give a beautiful lustre. Lustre 
can also be given to carefully finished surfaces 
by applying a small quantity of thinned var- 
nish, shellac or " fillers " by a cloth, and care- 
fully and thoroughly I'ubh'mg.—Comstock's "In- 
terior and Interior Details." 
|3ractical ^ints. 
Electric Wire Covering-.— M. Geoffrey, a wire 
manufacturer in Paris, has taken a patent for 
covering electric wires with asbestos. Experi- 
ments, which will be repeated officially, have 
proved that the copper can be burned without 
any spark being conducted outside. 
Archimedes.— Archimedes said: "Give me 
whereon I may stand, and I will move the uni- 
verse!" Ferguson, the celebrated astronomer, 
was accustomed to amuse himself by calculating 
that if, at that moment when Archimedes pro- 
nounced these words, God had taken him at his 
word, in furnishing him with a standpoint at the 
distance of 9,000 miles from the centre of the 
earth, with materials of sufficient strength, and a 
counterpoise of 200 lbs., this great geometrician 
would have required a lever of twelve Quadrill- 
ions of miles— 12,000,000,000,000,000— and a velocity 
at the extremity of the long arm equal to that of a 
cannon ball, to raise the earth one inch in 2.700,- 
000.000 000 years. 
Aluminium Silver.— Is made by melting to- 
gether one part of silver with three or four of 
aluminium, and is very valuable for articles in 
which one of the main objects is to obtain light- 
ness, such as the instruments used for marine 
observations. Octants and sextants of this alloy 
have been received with great favor by practical 
navigators. Those parts of such instruments 
which, if made with other metal, would weigh 
four pounds, will, when made of the above alloy, 
only weigh one pound. Mechanics like to work 
this alloy, as it can be turned and filed away, 
which is not the case with the pure aluminium 
which is too soft, and, as no doubt all know who 
have worked this interesting metal, it has the ob- 
jectionable property of sticking to the file. 
Atosorbtion of Metal by Tin.— When an 
alloy of lead, tin, or other metal is made with 
sodium in a melting pot, great care must be used 
in subsequently freeing the melting pot of every 
trace of sodium before using it for melting tin 
in with a view of tinning copper or bronze arti- 
cles, otherwise these articles when placed in the 
melted tin will be rapidly eaten away. This has 
been recently proved by accident, but it might 
have been expected from known facts concerning 
sodium alloys, which were long ago pointed out 
by Mr. Mallet, who showed, among other things, 
that if a strip of iron be coated with sodium 
amalgam and dipped into a pot of say molten tin, 
the iron will disappear faster than it can be put 
to the bottom of the pot. 
EXCHANGES. 
Only those who are >'£'(T:r/j' subscribers, and whose names 
are entered on our books have the privilege of inserting ex- 
changes. 
Exchanges must be on separate slips of paper or postal 
cards. If mixed with business matter in letters or cards they 
are filed away and never reach the printer. 
ICxchanges must not exceed thirty words. 
Buying and selling belong to the advertising department. 
We reserve the right to omit the exchange column, when 
we have not room for it, and the amount of space at our dis- 
posal will regulate the number of insertions given to each 
excJiauge, the preference being always given to those v/ho 
have not previously used our columns. 
Wanted engraver's tools with book of instructions, for a 
Victor Press, with cabinet, 2 type cases, type, ink roller and 
furniture complete ; perfectly new. L. Warren, 72 Cumber- 
land St., Brooklyn, N. Y. 
A Fletcher Foot-Blower, cost $5, as good as new ; will 
exchange for a Cushman, 2 in. or up scroll chuck, or other 
make; will give a satisfactory trade on the difiFerence in 
price, if any. Louis Lutz, St. Clair Street, Toledo, O. 
I have a lot of " Galaxy " (magazines) which I would 
like to exchange for an air rifle in good condition, a collec- 
tion of birds' eggs, or offers. W. B. Greenleaf, 480 
La Salle Ave., Chicago, 111 
