16 THE YOUNG 
Ink for Copying- Pads.— An ink which will 
yield a hundred or more copies from a gelatin 
pad may be made by dissolving rosaniline in a 
•cold saturated solution of oxalic acid. It must be 
allowed to dry spontaneously. 
To Polish Steel.— Mix half a pound of fine 
flour of emery powder with the same quantity of 
.soft soap, and add a small piece of soda. Simmer 
'this over a slow fire for two hou»s, to extract all 
the moisture. Rub on with flannel, and finish 
with plenty of dry whiting. 
Fastening- Knives in Handles.— A writer in 
the English Mechanic tells us that knives with 
tangs should be put into a handle with powdered 
•alum, the tang made hot as for resin. Let the 
handle be wood, iron, ivory, bone, or horn, it will 
Ibe immovably fixed unless the handle is split, and 
iar more cleanly than resin. 
Silver Solder.— Writing to the English Me- 
>chanic, T. Fletcher condemns the addition of 
brass to this alloy, and says: "The only satis- 
factory silver solder I have ever used is 11 parts 
flne silver and 13 parts copper. If brass is used, 
the solder burns with a blov/ pipe flame, and runs 
badly, making very poor and unsatisfactory work. 
The alloy given above is as tough as charcoal 
iron, and is always to be trusted. It never burns, 
and is as fluid as water when melted. 
NOTES AND QUERIES. 
Queries. 
42. In a journal recently started, and which 
makes great pretensions to scientific accuracy, 
the American inch is given as 39.381 metre. I 
always supposed that the American inch was the 
same as the English inch. How is it ? Metee. 
43. I bought a bottle of " silvering fluid " which, 
when applied to brass stair rods, gives them a 
Tery bright, silvery appearance, but after a time 
they become dull. What can I do to keep them 
bright ? Brass. 
44. I have a flne oil painting which has been 
varnished and spoilt. How can I remove the var- 
nish without spoiling the painting ? Amateue. 
Answers. 
45. Metee (42). The British and the American 
inch are the same, and accoixling to the latest de- 
terminations the ratio of the inch to the metre 
Is : Metre= 39.37043 inches. Some years ago a state- 
ment was made that the American foot was not 
the same as the English foot, and this error has 
•crept into several scientiflc books. It has been 
frequently contradicted, but occasionally it ap- 
pears again. Another origin for this singular 
■error is the fact that some years ago Congress 
passed an act legalizing the metre, and in that 
act it was stated that the metre should be taken 
as 39.38 inches. It is very evident, however, that 
this act, so far as it went, legalized an American 
metre, not an American inch. At the same time 
we believe that the acknowledged metric standard 
is a copy of the French metre, and this being the 
case, we have an anomalous condition of things, 
there being actually two standards in this country. 
45. Beass (43). Your " silvering fluid " is proba- 
bly a solution of mercury in nitric acid. It does 
not leave a coating of silver, but of mercury, and 
this will tarnish in spite of all you can do. If you 
use a silvering fluid containing pure silver, and 
then varnish the articles with a very pale varnish, 
they will remain bright a long time. 
SCIENTIST. 
EXCHANGES. 
Thos. D. Adams, Franklin, Pa., will exchange a 
$25 lawn mower, $60 coffee roaster, type, cards and 
books, $60 ; poultry journals, $10; 2 cocker spaniels, 
$30; 1 pair do., $80, and 1 pair $60; for key check 
outflt, improved model press, or offers. 
To exchange, 270 foreign stamps, many new and 
all different, and a boy's printing press, size, in- 
side chase, 3x4% inches, worth $9, for books, mi- 
croscope, or offers. Henry J. Bott, La Fargeville, 
Jefferson Co., N. Y. 
Wanted, a printing press and type ; state what 
is wanted in exchange; "Official" preferred. A. 
Campbell. Derrick City, McKean Co.. Pa. 
Dumb bells of all sizes, to exchange for most 
any thing ; send for circular containing weights 
of them to J. P. Donohue, Box 7, Davenport, Iowa. 
A Lozo -pendulum board (lined with genuine 
billiard cloth), consisting of ring toss, bagatelle, 
pockets, and ten pin, to exchange for parlor 
magic, aboriginal relics, or offers, T. C. Gard, 
Frankfort, Indiana. 
Wanted, scientiflc books and papers, micro- 
scope, drawing instruments, telephone, stamps 
and coins, in exchange for scroll saw, type, cards, 
revolver, shot gun, magazines, scientiflc books, 
or almost anything. W. L. Goodsell, Bath, N. Y. 
A pair of New York Club skates, worth $3.50, 
also coins, minerals and postage stamps, for 
books or offers ; correspondence invited. E. F. 
Greene, P. O. Box 889, Bath, Steuben Co., N. Y. 
A nice marine oil painting, ready framed, worth 
$5.00 ; state what is offered in exchange. C. Ham- 
mond, Artist, P. O. Box 47, Chatham, Barnstable 
Co., Mass. 
Photographic camera, one portrait and one land- 
scape tube, with chemicals complete, in exchange 
for medical books. J. Frederick Herbert, 1,324 
Poplar St., Philadelphia, Penn. 
What offers for i Household Microscope, one 8 
shot breech-loading carbine, 1 new 7 shot pistol 
and cartridges, 1 small gold watch, l small gold 
chain, l violin and case, one new darning machine. 
Lock Box 147, Tarboro, Edgecombe Co., N. C. 
Back Nos. "Penman's Art Journal" for 1879; 
Gaskell's.Compendium, $1 ; Coe & Shells' Pen and 
Ink Drawing, 25c. ; Pettengill's Fortune Teller, 
40c. ; Hand-Book of Business, 25c. ; in exchange 
for microscope, printing press, or offers- M. B. 
Moore, Morgan Station, Ky. 
Trump's and Eussel's scroll patterns, worth 
$10; for large lenses preferred. H. J. Peters, 
Eogersville, Ohio. 
Lessons in Standard Phonography given in ex- 
change for a printing press, lathe, scroll saw. 
scientiflc books, hammock, or offers. Phono- 
grapher. Box 331, Topeka, Kans. 
Wanted, chemical apparatus, in exchange for 
"Phrenological Journal," $2, and the last six 
numbers of "American Agricaiturist," 75 cents, 
of 1879. T. P. Potts, Canonsburg, Pa. 
Land and fresh water shells, birds eggs, min- 
erals, fossils (correctly named) or books. Gray's 
"How Plants Grow," Pope's "Linear Perspective 
Drawing." in exchange for a Multum in Parvo 
Collecting Box (for eggs). H. Bussell, Grassy 
Cove, Cumberland Co., Tenn. 
To exchange cocoons of the Atticus Cecropia for 
those of other rare moths, coins, stamps, trilo- 
bites, etc. Harry L. Shively, 680 N. Delaware St., 
Indianapolis, Ind. 
To exchange for offers, good second-hand set of 
brass band instruments: 2 E-flat cornets, 2 B-flat 
cornets, 3 E-flat altos, 2 B-flat tenors, 1 B-flat bass, 
1 E-flat tuba. David P. Thomas, Bellmore, Ind. 
To exchange, a book, "Linear Perspective," 
perfectly new. also several other books ; state 
offers. S. B. Wilson, Lenoir, Caldwell Co., N. C. 
For exchange, magic lantern, 4 in. condenser, 
28 slides, with gas bags and burner, also lamp ; 
for printing press, gun, or anything, E. F. Youngs, 
Penn Yann. N. Y. 
