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. 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. 22-12-inch guns. 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. HERE'S A FEW OF THE PARTS NAMED-THERE ARE 497 IN ALL. 278-Refrigerating room. 358-Exhaust air from dynamo room. Practical Books Just Ready-Centrifugal Fans, by J. H. KINEALY. M. Am. Soc. M. E. Dealing with their designing, construction 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 zinc. All parts where it is desired the Care and Handling of Electric Plants. Twentieth Century BY ANGUS SINCLAIR COMPANY Newly Published and is the PROFUSELY ILLUSTRATED. CONSULTING LOCOMOTIVE ENGINEERING Mention The Technical World. Compendium of Drawing, CYCLOPEDIA 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. OSWALD GUETH, M. E., Consulting Engineer, Technical Editor of "Cold Storage INTRODUCTORY OFFER NOT GOOD AFTER FEBRUARY 28th PROF. E. KENISON, 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 PROF. W. H. JAMES, M. I. T. Working Drawing PROF. C. L. GRIFFIN, formerly Pa. State College Machine 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 Compendium of Drawing, as advertised in The Technical ΟΝ 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 Chairs Telephone Central 4073 174 Wabash Avenue A. H. Andrews Co., Chicago. YOU CAN MAKE $3 TO $10 A DAY KEROSENE OIL ENGINE Stationary, Marine, Portable. Send for Catalog. Int'l Power Vehicle Co., 379-81 Dearborn St., Chicago THE CALCUMETER ADDS MULTIPLIES ETC. SERVICEABLE, SMALL, $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 SOLD ONLY ON ITS 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. |