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Are you worried by any question in Engineering or the Mechanic Arts? Put the question into writing and mail it to the Consulting Department, TECHNICAL WORLD MAGAZINE. We have made arrangements with the American School of Correspondence to have all such questions answered by members of its staff of Instructors. If the question asked is of general interest, the answer will be published in the magasine. If of only personal interest, the answer will be sent by mail, provided a stamped and addressed envelope is enclosed with the question. Requests for information as to where desired articles can be purchased will also be cheerfully answered,

Soldering Aluminum What is a good method of soldering aluminum?-J. T. K.

Difficulty insoldering aluminum arises from the fact that an oxide forms on the surface of the heated metal. The trouble may be overcome by making a solder of tin (four parts) and zinc (one Dart), with stearic acid as a flux. Coat the aluminum with this mixture moving

bit back and forth The film of oxide can then be cleaned off and the coated surface easily soldered.

grayish white powder. If the material is weighed before and after the treatment, the loss in weight will be the amount of vegetable fiber present. This method, however, can be used with only certain classes of goods, and is not as accurate or satisfactory as the following method:

Weigh carefully a small piece of material and boil it for four or five minutes in a four per cent solution of caustic soda. At the end of this period the wool will be completely dissolved by the caustic soda ; and if the weight of the dried residual material is subtracted from the original weight of the cloth, the loss will represent the weight of wool or animal fiber present.

Separating Cotton and Wool How can cotton and wool, mixed together in a piece of cloth, be separated ?-S. H.

There are two methods of separating wool and cotton, which are based on the action of acids and alkalies on cotton and wool. Acids completely destroy cotton or vegetable fiber, with little, if any, destructive action on wool; while alkalies will destroy wool or animal fibers and have no destructive action on cotton. If a cloth containing both cotton and wool is saturated with dilute sulphuric acid, and dried, without washing, at a temperature of 100° C., and then rubbed briskly between the hands, the cotton, which has become carbonized, will fall out as a

Arc Crucible Furnace on A. C.

Incandescent Circuits 1. Would you please let me know if it is possible to use an experimental arc crucible furnace on the alternating incandescent circuits used in the residence parts of the city?

2. Also please let me know if it is necessary to use any resistance coils, and the best way to wire for the furnace. - B. R. R.

1. A small furnace could undoubtedly be operated from the lighting circuit with entire satisfaction.

2. It would probably be better to use a resistance—or, better still, a reactance —for regulating the current. The best

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When you speak of a “ten-cent cigar,” you mean a cigar that costs you ten cents.

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Everyone-whether living at home or abroad-in town or country--can send their savings to this strong bank by the use of our carefully worked-out system of Banking by Mail.

The same cigar is to the manufacturer a' $40 per M.," or 4c. cigar, to the jobber a “$50 per M.," or 5c. cigar, and to the retailer a $60 per M.," or 6c. cigar.

Intrinsically that cigar is worth as much when the manufacturer appraises it at $40 per M. as it is when the retailer hands it over his counter as a "ten-cent straight." The difference between 4c. and 10c. is what it costs to get the cigar from the manufacturer to you along the old-fashioned trade turnpike with three coll gates.

Now, suppose you go to the maker of your cigars and say to him: “Sell me my cigars at wholesale and I'll take them home myself across lots."

"Oh, no," he will reply, "that wouldn't be fair to the retailer who has bought my cigars to sell at retail price."

I am a maker of cigars who has never sold a cigar to a jobber or retailer to sell again. Hence I am under no obligation to "the trade." I invite the patronage of the man who objects to paying for the privilege of allowing a retailer to sell him a cigar- who wants to buy his cigars at cost, without the arbitrarily added expenses of the jobber and retailer. To prove that I actually do sell my cigars at wholesale prices I offer them under following conditions:

MY OFFER IS:-1 will, upon request, send one hundred Shivers' Panatela Cigars on approval to a reader of


Panatela The Technical World, express prepaid. EXACT SIZE He may smoke ten cigars and return LAND SHAPE the remaining ninety at my expense if he is not pleasd with them; if he is pleased, and keeps them, he agrees to remit the price, $5.00, within ten days.

The fillers of these cigars are Clear Havana, of good quality, not only clear, but long, clean Havana — no shorts or cuttings are used. They are hand made by the best of workmen. The making has much to do with the smoking qualities of a cigar. The wrappers are genuine Sumatra.

In ordering please enclose business card or give personal reference, and state whether mild, medium or strong cigars are desired.

HERBERT D. SHIVERS, 913 Filbert Street, - Philadelphia, Pa.


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Mention Technical World Magazine

method of wiring and controlling the P the push, and C the battery. In Fig. 2 current would, however, depend on the the two bells are connected across the size of the furnace you wished to install. circuit in parallel. Bells connected in

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The New Universal Encyclopedia is revised up to date, giving the most accurate information on all subjects. The set is in eight volumes, bound in red library cloth, stamped in gold-a handsome, well-made set of books, worthy of a place in every home. There are 4,100 double column pages, with 2,000 text illustrations, beside a complete series of maps in colors, covering the entire world. It treats of every subject of general interest-from politics to polar exploration, from medicine to mechanics. It has been compiled by editors of the highest standing, and is guaranteed to be authoritative from A to Z. Compare it with reference works costing four times the price of this one-and prove this statement for yourself.

The Books and Magazine at a Bargain We have secured control of a limited number of sets at less than the actual cost of printing, and so long as these sets last, we will offer them in connection with a year's subscription for the Technical World at a price so low that it will make this the most extraordinary book bargain of a decade. The Universal Encyclopedia sells for $16.00 a set ; the Technical World is $1.00 a year;. but we cut the price of both combined to the exceptionally low price given below. SEND US THE COUPON

TECHNICAL WORLD, Chicago : from this advertisement, properly filled out (without any

Send me, at your expense, a set of the money), and we will send you a set of the New Universal

New Universal Encyclopedia, and enter Encyclopedia, express prepaid, for seven days'examination to

my name for a year's subscription for the be returned if not satisfactory. At the same time we will enter

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isfactory, I will send you 50 cents in seven If you decide to accept the books send us 50 cents in seven days

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If not satisfactory, I will return them. books and the Technical World. This offer saves you $9.50 and gives you this Encyclopedia and the Technical World for a little more than half the price of the books alone. Better take advantage of this at once, as this offer may not be repeated.


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Cyclopedia of Modern Shop Practico. A Practical Manual of the Best Modern American Methods in all Lines of Shop Work and Allied Branches of Mechanical Industry. Four Volumes; 3,000 pages, 7 by 10 inches. Illustrated with over 2,500 half-tones and explanatory diagrams. Indexed. Published by the American Tochnical Society, Chicago, Ill.

date, representing the latest and best of American methods, and being based on the most careful study, by acknowledged authorities, of actual shop needs and conditions. To read it, means to qualify for

the very highest kind of service. It THERE can be no such thing as “dry rot” means becoming intimately acquainted for any workman fortunate enough to with the best in American practice; it own this set of books. Be he foreman, means mastering those methods which journeyman mechanic, or apprentice, he have been the basis of America's material will find in it a key to progress and ad- success in competition with other nations, vancement. The CYCLOPEDIA OF MODERN and which have made the American SHOP PRACTICE was conceived in the workingman the most intelligent, the spirit of helpfulness, and has been pre- most efficient, and the best-paid workingpared throughout with a view to meeting man in the world. The appearance of the daily needs of the workingman as such a work from the press is in itself they arise under the conditions of actual the rendering of a public service worthy practice. And most admirably it fulfills of generous support; and we predict for its mission. To most men, a cyclopedia the CYCLOPEDIA OF MODERN SHOP PRAClooks formidable ; but to master this one, TICE, as its intrinsic merits become it will be found, is well within the power known, an increasing popularity, not only of the average wage-earner, and does not among workmen who are ambitious to require the elaborate formula of the make the best of their opportunities, but mathematician or the costly training of also among employers who take any apthe technical school. If knotty problems preciative interest in the welfare of their arise or obscurities are found, the Con- employees. sulting Privilege—which is given free for The field covered by the work is not one year to each purchaser—will instant- confined, however, within the walls of the ly bring the assistance of experts to clear “shop," so called, but takes in almost away all difficulties.

every branch connected directly or indiThis invaluable work stands head and rectly with machine shop practice, such shoulders above every other on Shop as the designing of machinery, forging, Practice which has yet appeared, not only pattern-making, foundry work, tool-makin its breadth and variety of scope, con- ing, sheet-metal work, tinsmithing, boiler venience of arrangement, and adequacy work, making of shop drawings, etc. The of treatment of each topic, but also in its reader is put abreast of the very latest thorough adaptation to meeting the wants progress by such chapters as those on the and solving the problems that are con- Turbine, Gas and Oil Engines, Automotinually arising in actual practice in the biles, Elevators, Electric Wiring and shop. It is, moreover, thoroughly up-to- Machinery, etc.

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