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THE VERANT IN USE.

graphic objective; and, on the other hand, the lens is free from any deformation for a diaphragm distant 27 millimeters (1.06 inches) from the nearest lens surface, the rotating center of the observing eye having to be placed at that point.

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These different conditions will result in a normal eye view instead of the small photograph, a distant image of the latter being free from any deformation (if the eye be placed at the point of no deformation), and fulfilling the same conditions as to apparent size, shadows, and relative distinctness as in the case of the objects being inspected from the objective of the photographic camera. The impression thus produced by the small photograph will be much more true to nature; and the main consequence will be an unconscious production of a true image agreeing with the different marks observed. The photograph as observed through the apparatus will therefore produce quite as plastic effects as in the case of being regarded with both eyes through a stereoscope.-DR. A. GRADEN WITZ.

Mention The Technical World.

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22-12-inch guns.
23-Sighting hoods-11-inch armor.
41-Conning tower-9-inch armor.
42-Rapid fire guns-1 pounders.

63-Upper fighting top.

69A-Code signal-"We can defend ourselves."

70A-Speed cone-"Full speed ahead." 193-6-inch guns.

Mention The Technical World.

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HERE'S A FEW OF THE PARTS NAMED-THERE ARE 497 IN ALL.

278-Refrigerating room.
291-Crew's hammocks.
313-Broadside torpedo tubes.
320 Submarine mines,
336-12-inch shells.
344-Upper dynamo room,

358-Exhaust air from dynamo room.
362-Coal bunkers.

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Practical Books

Just Ready-Centrifugal Fans, by J. H. KINEALY.

M. Am. Soc. M. E. Dealing with their designing, construction
and use with numerous Formulas, Illustra-
tions and Tables.

Suitable for architectural and engineering drawings.

8 NEW ALPHABETS.

Ninth Thousand.

By Mail 50c.

Question 2: How can I make an electrogilding bath which gives a red color like 14or 18-carat gold?-J. V. C.

Answer 1: Dry cells are sold at such a low price that it does not pay an individual to spend his time in the manufacture of a cell. A dry battery may be made in the following manner :

A jar of the desired shape is made of zinc; heavy sheet zinc should be used and bent into the required form, then soldered in such a manner that it forms

Spon & Chamberlain a jar. It will be found difficult to solder

Publishers TECHNICAL BOOKS
T. W., Liberty Building, NEW YORK

zinc. All parts where it is desired the
solder should stick should be carefully
cleaned by scraping, and clean chloride
of zinc used as a flux. The zinc should
have a brass binding-post soldered to it.
The other electrode is usually carbon,
and should have a similar binding-post
fastened to it.

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Care and Handling of Electric Plants.
With very useful table, formulas and
suggestions and 66 original drawings.
In limp leather
Price $1.00

Twentieth Century
Locomotives

BY

ANGUS SINCLAIR COMPANY

Newly Published and is the
Best Book on
Railway Machinery
Contains
ever published.
chapters on Elementary
lessons on first principles;
steam and motive power;
workshop operations; loco-
motive boiler construction;
compound locomotives;
valve motion; machine tools
and shop appliances, and
on nine other subjects.

PROFUSELY ILLUSTRATED.
Contains 670 pages, 6x9 inches.
PRICE, THREE DOLLARS

CONSULTING
DEPARTMENT

LOCOMOTIVE ENGINEERING
Department T, 136 Liberty Street
NEW YORK

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Mention The Technical World.

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Compendium of Drawing,

CYCLOPEDIA

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A COMPLETE

For the Library, the Shop, the Student

FOR EXAMINATION

REGULAR price, $10.00, reduced nearly

one-half in order to introduce the work. No more comprehensive treatise on drawing ever published. $25.00 would not buy separate volumes covering the subjects.

Practical test questions combine the advantages of a text-book with a Cyclopedia of Drawing.

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OSWALD GUETH, M. E., Consulting Engineer, Technical Editor of "Cold Storage
and Ice Trade Journal," New York, says: "I consider the 'Compendium of Drawing'
very thorough and complete for home study, and of excellent value for reference."

INTRODUCTORY OFFER

NOT GOOD AFTER FEBRUARY 28th

PROF. E. KENISON, M. I. T.
PROF. H. W. GARDNER, M. I. T.
PROF. D. A. GREGG, M. I. T.
PROF. W. H. LAWRENCE, M. I. T.

FRANK CHOUTEAU BROWN, Arch., Boston

Part II

BOTH VOLUMES sent free on approval (express prepaid). Keep them five days. If satisfactory send $1.00 and $1.00 per month for five months thereafter. Otherwise notify us and we will transfer them absolutely free. They have a permanent utility that makes them a desirable acquisition to every library.

LIST OF AUTHORS AND SUBJECTS

Part I

Mechanical Drawing
Shades and Shadows
Rendering in Pen and Ink
Perspective Drawing
Arch. Lettering

PROF. W. H. JAMES, M. I. T.

Working Drawing
Mechanism
Design

PROF. C. L. GRIFFIN, formerly Pa. State College Machine
WM. NEUBECKER, N. Y. Trade School, Sheet Metal Pattern Drafting
Tinsmithing

AMERICAN SCHOOL OF CORRESPONDENCE

CHICAGO, ILL., U. S. A.

Mention The Technical World.

Name....

.....CUT OFF HERE.

American School of Correspondence, Chicago:

St. and No..

City..

State

Please send me free, on approval (express prepaid), one

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Compendium of Drawing, as advertised in The Technical
World, February.

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N receipt of an inquiry from a prospective purchaser we asked how his attention was called to our machines, and here is his answer: "We have one of your machines and want another." ¶ If a machine does good work and has the lasting qualities so that your repair bills are reduced to the minimum, and requires ordinary skill to operate and is easier and quicker to adjust than other tools, you will want to know about it, so write for catalog.

Bignall & Keeler Mfg. Co.

Edwardsville,

Illinois

From Makers
Office Desks

Chairs
Tables

Telephone Central 4073 174 Wabash Avenue

A. H. Andrews Co., Chicago.

YOU CAN MAKE $3 TO $10 A DAY
Fitting glasses for us. Big profits.
Our 24-page FREE EYE BOOK
tells how. Write for it today.
JACKSONIAN OPTICAL COLLEGE, Dept. 936, Jackson, Mich.

KEROSENE OIL ENGINE

Stationary, Marine, Portable. Send for Catalog. Int'l Power Vehicle Co., 379-81 Dearborn St., Chicago

THE CALCUMETER

ADDS MULTIPLIES ETC.
RAPID, ACCURATE.

SERVICEABLE, SMALL,
PERFECT CONSTRUCTION.

$2500

CONSULTING DEPARTMENT-(Continued)

sulphite of soda and cyanide in the remaining 100 parts. Pour gold solution slowly, with constant stirring, into the phosphate solution, which acquires a greenish or yellow tint. Now add solution of bisulphite and cyanide promptly, and the solution becomes colorless. If this does not give deep enough red, use a gold cyanide solution with the addition of a little copper cyanide.

3

If you are interested in any kind of investment, Oil, Mining, Plantation, Industrial, Lands, Stocks, Bonds, Mortgages, etc., send us your name and address and we will send you The Investor's Review for three months free of charge. A journal of advice for investors. Gives latest and most reliable information concerning new enterprises, Knowledge is power. Great opportunities come and go. Great fakes likewise. Get posted before investing Write to-day. INVESTOR'S REVIEW, 1580 Gaff Bldg., CHICAGO, ILL

Turbine Tube

Question: Kindly give me the necessary information how to design the turbine tube shown in the accompanying sketch. The tube is 8 feet in diameter and made of steel plate. What is the pressure against the sides of the tube at the different heights; and how thick shall the plates be to withstand the pressure, the allowable stress being 12,000 pounds per square inch?—C. IV. B.

High Water

300'

BE

Water Reservoir

Answer: The pressure at any crosssection of the pipe can be determined by multiplying the head in feet at that section by the factor .433. The greatest pressure on the first 300 feet length of pipe will be that due to the head of 18 feet. This corresponds to a pressure of 7.8 pounds per square inch. The greatest pressure on the last section will be that due to the total head of 55 feet, and is equivalent to 23.8 pounds. By use of the formula, the neces

AUTOMATIC CARRIER

CORRECT ADDITIONS MAKE EMPLOYEES
SERVICES VALUABLE.

SOLD ONLY ON ITS
MERITS
WRITE FOR CATALOGUE No 11 AND 10 DAY FREE TRIAL
THE MORSE & WALSH CO., TRENTON, N.J.

Months Free sary thickness of the tube can be de

termined:

-20

DXP

=

t= 2X SXE'

J

in which is the thickness in inches; D, the diameter in inches (96); P, the pressMention The Technical World.

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