112 
THE YOUNG SCIENTIST. 
pine. Oak, which is sometimes used, is heavy, 
and seems to liave a tendency to rust the tools. 
The runners may be of oak or other hard wood, 
capped with wlialebone. Pine is most suitable 
for the tills if the maker intends to veneer the 
inside. 
Black Coating- for Zinc— Dingler's Polytech- 
nic Journal states that M. Neumann has instituted 
a series of experiments to point out the best ma- 
terial to produce upon statuary or ornamental 
objects made of zinc a pleasing blackish coating, 
without impairing the effect of the natural color 
of the metal, as would be the case when an oil 
paint or varnish is used. The best results were 
obtained when nitrate of protoxide of manganese 
was employed. This salt, on being heated, is de- 
composed, yielding black peroxide of manganese, 
and the degree of heat required is not so high as 
to affect the zinc. The best solution for this pur- 
pose is fifty-four grammes of the salt in one litre 
of water. 
Preservation of Paste with Salicylic Acid. 
The souring and molding of paste used by book- 
binders and workmen in other trades, which, ac- 
cording to circumstances, occurs in about two or 
thx-ee days, may be entirely avoided, according to 
the statement of Herr P. Lung, by the addition 
and thorough mixture with the freshly-prepared 
paste of a few drops of salicylic acid. When thus 
treated, a paste may be kept for weeks in a heated 
room without losing its freshness, and even when 
it has by long standing become dry and tough, 
may be at once rendered fluid and serviceable 
by treatment with hot water. The addition of 
the acid does not, according to this author, af- 
fect the stickiness of the paste to any sensible 
degree. The above item will, doubtless, prove 
serviceable likewise to all who have only occa- 
sionally to make use of v^QtQ.— Gewerhehlatt aus 
Wurttemherg. 
EXCHANGES. 
Only those who are ^mr/)/ 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 letters or cards they cannot 
be used. 
Exchanges 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 
exchange, the preference being always given to those who 
have not previously used our columns. 
Will exchange, for printing outfit or shot gun, 
6 years Nos. of Scientific American, with Supple- 
ment of 1876, 545 foreign and U. S. stamps, Art of 
Swimming, Instruction in Shorthand, and other 
books. W. A. Smith, West Eandolph, Vt. 
Good Specimens of the 17 years' locust (17 year 
cicada), in exchange for anv kind of insects, 
beetles, moths, orbutterfiies. Harry C. Beardslee, 
Painesville, Lake Co., Ohio. 
Insects and butterflies from China: state what 
is offered in exchange. Edward Laurent, 621 
Marshall St., Philadelphia, Pa, 
I have a four-legged and four-winged one- 
headed chicken, in alcohol, which I should like to 
exchange for a good breech-loading shot gun, or 
for standard scientific books. A. H., Box 500. 
Albion, Ohio. 
Wanted, scientific books, minerals, fossils, and 
Indian relics, in exchange for minerals, fos- 
sils, coins, old Continental and Federal money 
over one hundred years old (very rare), foreign 
stamps, A. W. Baily, Box 712, Atlantic City, N. J, 
Birds eggs, books, foreign stamps, a good ham- 
mock, and revolver, to exchange for birds eggs 
and works on birds. P. D. Brown. Gallupville, 
Schoharie Co.. N. Y. 
A magic lantern with eight slides, cost $5, and 
other things, to exchange for scientific books, 
chemicals, or chemical apparatus, etc. A Camp- 
bell, Box 31, Derrick City, McKean Co.. Pa. 
Idaho Mineral Specimens, for bound books on 
science, travels, history, biography, political, ma- 
sonic, and others that are instructive. J. P. 
Clough, Junction, Lemhi Co., Idaho. 
I have minerals (including fossils and den- 
trites), to exchange for minerals; also a papyro- 
graph outfit, without press (worth $25), for offers. 
W. H. Eastman, Hyde Park, Mass. 
Craig's Simple microscope and three objects, 
$2.50 ; 155 rare stamps in small album, 1 font of 
type; "Illustrious Mechanics," $1; "Northern 
Lights," $1.50; for coins and curiosities. Geo. K. 
Fischer, 729 North 6th St., Phila. 
Klose's celebrated " School for the Clarionet," 
new, $3 ; will enchange for telescope, microscope,, 
piccolo, books, or offers. Rush Holbrook, Wone- 
woe. Juneau Co., Wis. 
One or two handsomely mounted red deer heads, 
attractive ornaments for any dining-room or hall, 
for microscope, telescope, sporting implements, 
camping outfit, scientific books, or offers. R. B. 
Hough, Lowville, Lewis Co.. N. Y. 
A new E-flat solo cornet, cost $22, for a self-ink- 
ing printing press and outfit of same value and 
condition, also B-flat clarionet, books, papers, 
magazines, etc., for offers. C. W. Hughes, P. 0. 
Box 96, Shreve. Ohio. 
Hope's Manual of Sorento and Inlaid Work, 
cloth edition, price $1.25 ; would like to exchange 
for books on aquaria postage stamps, hammocks, 
or almost anything. G. Keppel, Zeeland, Ottawa 
Co., Mich. 
A new one horse power horizontal steam 
engine, in complete running order, worth $60, 
for a first class coal stove, watch, or offers. Geo. 
L. Lamson, La Fargeville, Jeff. Co., N. Y. 
A handsome Young America self-inking print- 
ing press, chase 332 X 4X inch, with 5 founts of 
type, 300 cards, and outfit complete, for a good 
wood-turning lathe, or offers. E. McLean, 443 
Clermont Ave., Brooklyn. 
Telescope, microscope, drawing instruments, 
and other things, in exchange for printing press- 
and outfit, or offers ; wanted, cards, type, etc. 
Ewing McLean, Green castle, Ind. 
I should like to exchange birds eggs with any 
one living in the far West. South, or in foreign 
countries. Wallace Ross, Lock Box 97, Rutland, 
Vermont. 
I have some good specimens of Pentremites 
from the sub-carboniferous formation, that I 
would like to exchange for books, H. Russell, 
Grassy Cove, Cumberland Co., Tennessee. 
Bonanza printing press, with three fonts of type, 
and assortment of blank cards ; value of outfit 
$7.25; would like rifle, books, or offers, Geo. R. 
Simpson, Janesville, Bremer Co., Iowa. 
Fine cabinet for sale or exchange ; polished 
walnut and maple, 27 drawers, 3 closets, all locked ; 
7 ft. X 5 ft. X 19 inches ; for any kind of specimens. 
W. W. Stockton, Box 190, West Chester. Chester 
: Co., Pa. 
