116 
THE YOUNG SCIENTIST. 
one hundred and sixty parts of pipe-clay, and 
proceed as above directed. Another process is as 
follows: Take fifteen grammes of blue vitriol, 
twenty of calcined soda, mix them well with 
thirty-two cubic centimetres of glycerine, and 
mix the paste obtained with eighty grammes of 
pipe-clay. It is then ready to be applied as before 
stated. 
The Obelisk in the Central Park, New York, 
weighs two hundred tons, or is equivalent to 
the weight of about eight hundred and twenty 
millions of Esterbrook's Ladies' Pens. 
EXCHANGES. 
Only those who are yearly 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 inseriions given to each 
exchange, the preference being always given to those who 
have not previously used our columns. 
To exchange, Hugh Miller,s "Cruise of the 
Betsey," and " The Old Eed Sandstone," cloth 
bound geological books, for lathe, hammock, or 
"Gray's Manual of Botany." Gus. C. Spaeth, 
Mt. Carmel, Ills. 
F. F. F., Lock Box 83, St. Johnsbury, Vermont, 
would like to exchange or correspond with per- 
sons interested in mineralogy. Oology, phila- 
tology, Indian relics, books, entomology, numis 
matology, etc. 
Wanted, a good printing press and type ; state 
what is wanted in exchange. H. A. Kinney, 
Hamlin, Brown Co., Kansas. 
I have a printing press and outfit (cost $15) to 
exchange for books, microscope, tent, watch, or 
offers. Henry E. Jacobs, 59 Harvard Street, 
Boston, Mass. 
I have Yols. 2 and 3 of "Nests and Eggs of 
American Birds," to exchange for Vol. I of 
Young Scientist, or offers. N. B, Stone, Lock 
Box 9, Putnam, Conn. 
Wanted, a printing outfit or offers, in exchange 
for baritone cornet, air gun, and other things, a 
list of which will be furnished upon application. 
E. S. Nixon, Jr., Box 345, Chattanooga, Tenn. 
To exchange, minerals, ores, shells, papers, 
magazines, books, coins, stamps, for stamps, 
coins, minerals, stylographic pen, telephone, etc. 
A. M. Beveridge, P. 0. Box 854, Appleton, Wis. 
Will exchange minerals for other minerals; 
state what specimens you desire. E. A. Eefsny- 
der, Phcenixville, Chester Co., Pa. 
Wanted, a good powerful second-hand micro- 
scope; forward engraving of instrument, stating 
price, or what is wanted in exchange. L. D. 
Snook, Barrington, Yates Co., N. Y. 
Wanted, botanical specimens of Western, West 
Coast, and Southern ferns, in exchange for 
Northern species ; lists exchanged. H. N. John- 
son, Coeymans, N. Y. 
Wanted, copy of "Snowball's Elementary Na- 
tural Philosophy." M. B Tausy, Harrisburg, Pa. 
k new 2x4 engine, worth $60, for a first-class 
bicycle ; also a watch, revolver, and gas stove, for 
a 6x9 printing press, tvpe, or offers. Geo. L. 
Lamson, La Fargeville, N. Y. 
To exchange, specimens in botany, oology, etc., 
for those in other localities; botanical corres- 
pondents desired. Arthur Fairbanks. St. Johns- 
bury, Vt. 
To exchange, for other books on scientific and 
industrial subjects, "Moore's Universal Assis- 
tant," " The Young Mechanic ; " both quite new. 
Fred. Whitehead, Box 55, St, Augustine, Fla. 
A German microscope, with 3 objectives and 5 , 
eye-pieces, condensing lens, etc., resolving Pleu- 
rosigma angulatum, will be exchanged for a 
first-class spectroscope. Clarence L. Speyers, 
50 West 17th St., New York. 
I have a fine concert harmonica, 20 notes, with 
case, but little used, that I will exchange for Vol. 
3, of the Young Scientist. Charlie O. Wells. 
Hatfield, Mass. 
To exchange, birds' eggs and minerals, for 
minerals, ores, and curiosities. H. G. Emery, 51 
Spencer St., Albany, N. Y. 
To exchange, for engine or offers, a pair of Bliss 
Telephones and 200 feet of copper wire. J. W. 
Grant, 402 Broad St., Newark, N. J. 
To exchange, a 233 octave chromatic xylophone 
for microscope, microscopical apparatus, scien- 
tific books, or offers. J. E. Moore, Box 81, New- 
castle, Ind, 
To exchange for offers ; a small lot of micro- 
scopic mounting apparatus. List on application 
to J. N. B„ Box 1468, N. Y. 
To exchange, books and Young Scientist, and 
trinkets, for other books, revolver, or stylo- 
graphic pen. Frank Bicknell, Humboldt, Iowa. 
Ancient petrified grain, Indian pottery, birds 
eggs, papers, magazines. Confederate money, 
fossils, minerals, to exchange for arrow-heads, 
Indian relics, Confederate, Continental, and 
other paper money. Fred T. Brinkerhoff, Box 
347, Neenah, Wis. 
Minerals, tricks, copper coins, book on pigeons 
and rabbits, Wilson School History, for book on 
experiments, or specimens, minerals, stamps or 
coins. P. E. Bradley, Box 305, Dunkirk, N. Y. 
Wanted, a second-hand screw cutting foot 
lathe, must be in good condition; state what is 
wanted in exchange, also size and make of lathe. 
G. A. Clark, Castalia, Iowa. 
To exchange, minerals, shells, fossil shells, 
birds eggs, etc., for minerals, shells, fossils, 
stuffed birds, birds eggs, and books. U. S. Grant, 
Des Moines, Iowa. 
Wanted, botanical correspondents for the com- 
ing season, also amateur correspondents in 
chemistry. L, Box 70, East Templeton, Wov. Co., 
Mass. 
Wanted, to exchange a well-equipped job print- 
ing outfit, for books or offers. Frank A. Nib- 
lack, Eockport, Ind. 
Will exchange for Vol. 2 of the Young Scientist, 
instructive books bound in cloth to the value 
of $1.50. Chas. H. Williamson, 293 Eckford St., 
Greenpoint, Brooklyn, N. Y. 
I have a new Munsen's battery, large size, which 
I wish to exchange for a good revolver or offers. 
Eobt. T. Boyle, 351 West 83d St., New York. 
Hair of American deer to exchange for diatoms, 
foraminifera. or other material. W. H. Osborn, 
Chardon, Ohio. 
To exchange, full instruction in short-hand 
writing, and birds eggs, for birds eggs, postage 
stamps, or offers. M. F. E., 51 Spencer St., Albany, 
N. Y. 
Wanted, specimens in geology, entomology, 
oology, etc., for those in other localities, also 
coins and a charm microscope (magnifies 1,000 
times) for one having a different view. J. H. 
Jones, Frankfort, N. Y. 
"History of Our Country," by Lossing, in six 
parts, price $15, to exchange for printing press or 
' offers. Frank Chandler, Waverley, Mass. 
