144 
THE YOUNG SCIENTIST. 
QUESTIONS AND ANSWERS. 
Drilling Glass.— In the number of the Young 
Scientist for August, 1880, page 100, you give a 
short note ou " Drilling Glass," and tell us how 
7tot to do it. Will you please tell us Jiow to do it? 
J./iS.— Tiiere are three ways of drilling glass: 
One is witii a diamond drill ; tlie second is with a 
soft metal drill ciiarged with sand or emery, and 
the third is by means of a steel drill. A liard 
steel drill, lubricated with sulphuric acid, or with 
camplior dissolved in turpentine, will cut glass 
very rapidly. We have frequently bored a hole a 
<iuarter of an incli in diameter through a thicli 
plate of glass by means of such a tool. Tlie dia- 
mond drill, tor iioies over a quarter of an incli in 
diameter, consists of an iron tube with splinters 
of diamond iirmly stuck into holes bored on the 
outer and inner edge of the tube. For small holes 
an iron rod charged with diamond powder an- 
swers well. Copper drills, made either of copper 
rod or copper tubing, according to size, answer 
well. They are kept charged with emery or 
sharp sand and water, and the drill should be 
guided by a block of wood cemented to the glass. 
The wood has a liole bored through it the exact 
sizt:* of the drill. This hole is placed exactly over 
the spot where the proposed hole is to be. and 
prevents the drill from slipping about. 
PowEK OF Eye-pieces and Objectives.— Can 
yoii tell me what is the standard of pi^wer for the 
different objectives marked a, b, c, d, e, etc. ? I 
have a microscope witli very good objectives and 
eyepieces, marked a and c, and I feel satisfied 
that the objectives will give good definition with 
much higher magnifying power than T now get. 
What power will I get if I procure a T> eye-piece ? 
^ns.— The values of the djfferent eye-pieces 
vary with different makex's, and this to such an 
extent that unless we knew who Avas the maker 
of your^microscope we could give you no accurate 
information on the subject. The eye-pieces 
made by Koss twenty years ago, as given by 
Brooke, Avere as follows: 
Name of Focal Magnifying 
Eye-piece. Value. Power. 
A 2*7 inch 3"7 times. 
B. - - 1*6 " 6 
c 1- " 10 
D -6 " 17 
E -4 " 25 
and tliis scale seems to have been pretty closely 
followed by most makers. So that a d eye-piece 
on the above scale would give jow a magnifying 
power rather more than one and a half times 
what you now get. 
EXCHANGES. 
Only those who are 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, wher 
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 alw'iys given to those who 
have not previously used our columns. 
Magic lantern, in good order, condensing lens, 2^^ in. 
diameter, 8 slides. For small photographic camera or offers. 
H. A. Giddings, 4 Union Place, Classon Ave., Brooklyn. 
Fifty canary birds, with and without crests ; fancy 
poultry, conch shells, strombus alatus. For small printing 
press, books on natural history, or offers. Frank Lattin, 
Gaines, N. Y. 
Printing press, type, etc., worth $13, for offers, E. G. 
Vogeley, loio Bradford St., Pittsburgh, Pa 
A good plain 7 shot revolver, 22 calibre, for a Students' 
inch or half-inch objective. Frank F. Colwell, Urbana, 
Ohio. 
Wanted, Printing press and type, in good order, chase 
6 X 10, or larger; will give hardware, tools, scroll saw, or 
designs. Chas. E. Little, 59 Fulton St., New York. 
Photo outfit, tools, chemicals and apparatus, etc., etc.; 
wanted scientific books, apparatus, etc ; send lists. A. B. 
Campbell, Box 59, South Dayton, Catt. Co., N. Y. 
Stuffed birds, insects or job printing (cards, labels, etc.) 
for mounted objects for the microscope. James P. Melzer, 
Milford, N. H. 
A ring stand, filtering stand, calcium light jet and a gas 
holder, holding one cubic loot, for a phonograph. D. P. 
Smith, 59 Park Place, New York. 
To exchange, Hugh Miller,s "Cruise of tlie 
Betsey," and "The Old Red 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, iiumis 
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 
oiTers. Henry E. Jacobs, 59 Harvard Street, 
Boston, Mass. 
I Imve Vols. 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. O. Box 854, Appleton, Wis. 
Will exchange minerals for other minerals; 
state what specimens you desire. E. A. Refsny- 
der, Phoenixville. 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 AVestern, West 
Coast, and Southern ferns, in exchange for 
Northern species; lists exchanged. H.N.John- 
son, Coeymans, N. Y. 
Warned, copy of " Snowball's Elementary Na- 
tural Philosophy." M. B Tausy, Harrisburg, Pa. 
A new 2x4 engine, worth $60, for a flrst-class 
bicycle ; also a watch, revolver, and gas stove, for 
a 6x9 printing press, type, 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 n 
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. 
