73 
THE YOUNG SCIENTIST. 
until it is all dissolved. Let it cool to blood 
heat; then add three liquid ounces of sulphuric 
acid. When cold it is ready for use. One cell 
of this battery is equal to six or eight tin can 
batteries. 
This battery you can keep for years, and 
when you want to use it pour in the fluid and 
it is ready. It starts with full force. 
H. A. Kinney. 
HamliUy Kansas, 
[The above is a very simple method of mak- 
ing a good battery, but it costs a good deal 
more than the tin can battery. Thin zinc does 
not last long in such a battery, and it is not 
always that a heavy zinc can be had for the ask- 
ing. Well burned coke will be found to give 
better results than ordinary charcoal. — Ed. A. 
J. M.] 
BOOK NOTICES. 
Hints to Plumbers and Householders. By 
W. L. O'Grady. With illustrations. New York: 
American News Company. 
The numerous cases of sickness which have 
recently arisen from defective sewerage, many of 
them terminating fatally, has called renewed at- 
tention to the system of plumbing usually pursued. 
This little book explains the best methods of secur- 
ing safety, and gives very complete figures of all 
the best arrangements in use. To the plumber it 
will be valuable, from the fact that it contains a 
great deal of useful statistical information and data 
in a compact form, while the householder must 
prize it from its clear and popular discussion of the 
general subject. 
EiXtiibition of National Academy of De- 
sign. — The fifty-third annual exhibition of the 
National Academy of Design is now open, and pre- 
sents a rich feast to lovers of art. It is generally 
conceded that the present exhibition exceeds in 
interest anything that has gone before it, and cer- 
tainly many of the paintings now on the walls de- 
serve hours and hours of continuous study. In 
the limited space at our command it would be im- 
possible to enumerate even the most prominent 
paintings on exhibition, while to single out a few 
would be invidious. We trust, however, that many 
of our young readers will visit the exhibition again 
and again, to see them and study them for them- 
selves, for we know of no way in which a few even- 
ings can be passed with greater pleasure, and cer- 
tainly of all the exhibitions now open to the public, 
none has a more elevating tendency. It is hardly 
necessary to say that the rooms are at the corner 
of Fourth avenue and Twenty-third street. 
EXCHANGES. 
In this column yearly subscribers who may wish 
to exchange tools, apparatus, books, or the pro- 
ducts of their skill, can state what they have to 
offer and what they want, without charge. Buying 
and selling must, of course, be carried on in the 
advertising columns. 
A good telegraph instrument, cost $7 50, for a 
couple of good books on chemistry, electricity, etc. 
H. B. Kinney, Hamlin, Brown County, Kansas. 
Wanted to exchange, a stencil outfit for a 
Barnes' scroll and circular saw, foot power; or a 
good battery for electro-plating; or an artificial 
incubator; or state what you have to exchange; 
reason for exchanging is the partial loss of right 
arm; all letters answered, Barton A. Whitsett, 
Box 115, Lebanon, Ind. 
A large number of minerals and fossils for ex- 
change. Persons wishing to exchange please send 
hst to W. H. Hughes, 47 Jeff. Avenue, Grand Eap- 
ids, Mich. 
Wanted in exchange for a second-hand scroll 
saw, treadle power and wooden frame, a good Ex- 
celsior microscope, or live box. Jos. G. Thorp, 54 
West Seventeenth street, New York. 
A set of chemicals and apparatus; also a set of 
wood engraver's tools, glass and instruction book, 
to exchange for a scroll saw and a microscope. The 
chemicals and tools cost nearly $40; will give a good 
trade. F. H. Jackson, Angelica, N. Y. 
To exchange, a Pope's air pistol for a set of carv- 
mg tools. L. Y. K. G., Box 317, Brookfield, Mass. 
Cigar machine to exchange for bracket saw or 
good microscope. Leonard Alexander, Linneus, Me. 
Wanted, a small turning lathe in exchange for a 
pair of telephones. J. C, care Young Scientist. 
Magic lantern, nine slides (two mechanical) in 
complete order, in exchange for good compound 
microscope. T. R. Barwood, Flatbush, L. I. 
A work on painting and wood finishing, value 
$1.50, to exchange for scroll saw patterns. E. F. 
Hanscam, North Barnstead, N. H. 
Gold watch (cost $150) in exchange for a good 
microscope. E. W., Box 4875, New York. 
Wanted, a xylophone in good condition; a Cen- 
tennial jig saw, bought in December, in exchange. 
C. B. Culver, 131 East Seventeenth St., New York. 
Back numbers of the " Youth's Companion," for 
the years 1876 and 1877, cost $1.75 a year; lathe, for 
Centennial bracket saw; or "The Speaker's Gar- 
land," Vol. 2 or 3. F. R. Miller, 750 East Fourth 
street. South Boston, Mass. 
Scroll saw wanted in exchange for handsome 
portfolio of six water color sketches. Address 
F. 8., care Box 4875, New York. 
Specimens of the marbles, granites and minerals 
of Vermont, in exchange for Western minerals, or 
good fossils; minerals and fossil woods from the far 
West 8i)ecially desired. Dr. H. A. Cutting, State 
Geologist, Lunenburgh, Essex County, Vt. 
Thorough and practical instruction in shorthand 
will be given in exchange for a microscope, with or 
without accessories, worth from $5 to $10. Address 
T. P. Wendover, 68 Christopher street. New York. 
Wanted, a small turning lathe, about 1^ inch 
swing, and 12-inch bed; must be well made; books 
and apparatus in exchange. R. M., care of this 
journal. 
Wanted, a copy of Holtzapfel's "Mechanical 
Manipulation." State what is wanted in exchange, 
E. W., Box 4875, New York. 
