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specification of the weight, and a draw- price, according as the work may be ing showing the dimensions and design found to be satisfactory or to leave someof the carpet to be made. All of these thing to be desired. specifications, as they might be called, are Finally, it may be added that at Tauris issued in duplicate, so that, when the car- there are about 2,000 persons employed pet is delivered, the payment is made in a similar way making carpets for exwith a premium or a reduction in the port.

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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 to have all such qu ions answered by a staff of consulting engineers and other experts whose services have been specially enlisted for that purpose. If the question asked is of general interest, the answer will be published in the magazine. 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.

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Making a Pipe Rack

161/2 inches and a width of 512. The I am constantly losing my smoking pipes.

dimensions of the lower shelf and the I should be very glad to have you give a brief brackets are indicated in the drawing. description of how to make some sort of a rack The rack may be made of oak, pine, to keep them in.-0. W. W.

maple or mahogany, as desired. Your question will be best answered by the accompanying drawing, the various parts being shown in section and to

The Lalande Cell
gether. The upper shelf may be built What chemical action takes place in the La-
wide enough to hold the tobacco jar, lande cell?—R. O.
match safe, etc. The dimensions of the The elements of this cell are two amal-
rack are, for the upper shelf, a length of gamated sheets of zinc, between which is

the inactive plate, con-
sisting of a compacted
mass of black oxide of
copper, all suspended in
a solution of caustic soda
or caustic potash of
about 1.16 specific grav-
ity. The electromotive

force of this cell is at 1023

first as high as 1.2 volts,
due to the free oxygen
in the copper oxide, but
when this is exhausted
the voltage falls to 0.82,
at which it remains un-

til all the copper oxide

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is reduced to metallic copper. Then a further drop in voltage occurs.

When this point is reached the cell should be regenerated by removing the copper plate, washing it with clear water, and exposing it to the action of the air at a temperature of 220° to 250° F. for an hour. The copper is thus oxidized to

the worm, B, which is surrounded by cold water, and finally issues at H as distilled. A baffle plate, F, may be located in the head of the still to prevent any water from being carried over mechanically in case the water in A should boil too violently.

In works where only a limited amount of pure water is required, it is sometimes the practice to condense direct steam from the boilers, or indirect steam that has already been used for heating purposes or otherwise. In this way a comparatively pure water is obtained, but its purity cannot always be depended upon, as oil, which is volatile with steam, is likely to get into it in various ways, and iron rust from steam pipes occasionally causes trouble.

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Electric Transformer copper oxide, and can be used with its

1: On an alternating current dynamo can original efficiency. The liquid also should a transformer be used to change the high elecbe replaced when it shows precipitate of

tro-motive force to a high amperage ? zinc hydroxide.

2: Can a motor or dynamo be wound with

same size wire on the field magnets as that The chemical actions are as follows: upon the armature, and would you get prac(1) Zn + 2NaOH = Zn(OH)2 +


tical results from this treatment? Na,.

3: Please explain what transformers are

used for.-H. A. (2) Na, + 2H,0= 2NaOH + H. (3) CuO + H, = Cu + H,O.

1: A transformer can be used to (4) Zn(OH)2 + Na(OH), = Na, change the high electromotive force of ZnO, + 2H,O.

an alternating current generator to low The liquid becomes a solution of

electromotive force, the current at the sodium zincate which permits zinc hy

same time being changed from small to droxide to settle out as a precipitate.

large in the same ratio. This is one of the great advantages of alternating current, that its electromotive force can be

stepped up or down at will by the transTo Distill Water

former, which is cheap, very simple in Will you please describe a small still for

operation, and very efficient. making distilled water?-H. L. B.

The still is shown in the figure. A still of this kind may be heated by direct gas flame or, what is better, by a steam coil inserted within the still, or by a

А steam jacket. The figure represents a cross section of such a still. The water in the still, A, is constantly kept at the level of the water in the condenser, B, by means of the cross connection, C. Steam is introduced into the jacket, J, The arrangement for doing this is through the valve, D, and escapes through shown in

shown in the accompanying sketch, valve E, and by properly regulating these where A represents the alternator, P valves, the water in A may be boiled represents the primary of the transformsteadily for hours. The vapor passes er, S represents the secondary, and LL over through the neck, G, condenses in represents the line. In case we wish

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to change the electromotive force from a Take a board that has been well planed, high value to a low value, the primary in size 58 by 28 inches. The board must coil P contains a large number of turns be perfectly level. For a padding for of fine wire, and the secondary a small this, in order that the balls may not roll number of turns of coarse wire. Sup- too easily, use burlap or old ingrain posing, for instance, we wish to reduce carpet. As a bulwark to keep the balls the voltage from 1,000 to 100; then there on the board, run a strip all around. will be 10 times as many turns in the Bore holes in the board, each pair of primary coil as in the secondary. holes being about one inch apart. Stiff

copper wire, five inches long, bent into shape, will make excellent arches. Some sort of heavy wood should be used for the mallets. The heads should be onehalf inch in diameter. Fit handles of suitable length, and wind the heads of the mallets with small copper wire. Ordinary marbles may be used for the balls.


Testing Quality of Steel Can you suggest an acid test for iron and steel?-H. R. J.

The piece of metal to be tested should TABLE CROQUET BOARD.

be filed smooth, or polished. It should

then be given a bath in dilute nitric or 2: There would be no particular sulphuric acid for from 15 to 20 hours, reason for winding a generator or motor

Next it should be washed in water and with the same size wire on both the field dried, when certain effects will be maniand the armature, and ordinarily the wire

fested according to the grade of the on the armature would be very much

metal. If a frosted effect is produced, larger than that on the fields. This

the steel is of the best quality ; inferior would always be true in the case of a

grade has a honey-combed appearance; shunt machine. In the case of a series

iron shows a fibrous structure in the diwinding, it might happen for some par

rection in which it has been worked. ticular work that the design would call for the same size wire on the fields as on the armature, but in case it did so this would be a mere coincidence.

Preserving Iron 3: The function of the transformer, How shall I preserve iron from rusting?as already explained, is to vary the elec

T. A. A. tromotive force, the current at the same First immerse the metal for several time varying inversely in the same pro- minutes in a solution of blue vitriol; then portion. If we have a high electromotive place it in a solution of hyposulphite force and a low current, this can be soda, acidulated with chlorhydric acid. changed to a low electromotive force and This coating, in color blueish, will protect high current, or vice-versa. The ratio the iron against all moisture. of the secondary electromotive force to the primary is approximately the same as the ratio of the number of secondary

Making Nitro-Glycerin turns to the number of primary turns in the transformer.

How is nitro-glycerin made?-A. H. H.

Ordinary glycerin is sprayed into a

vessel containing a mixture of nitric acid Table Croquet Set

and sulphuric acid in the proportion of

two parts sulphuric acid to one part I am handy with tools and like to make the things I use.

nitric. A combination of the glycerin Can you suggest how to construct an indoor croquet set ?-M. W. N. with the acids at once takes place with



cream is


the result that a

reach the next contour, and continue to formed on the surface. This is carefully step off such spaces. Joining these skimmed and then washed until all the points, such a line would be a purely surfree acid is removed. The product is a face line, would probably be very commodity ready for the market.

crooked and otherwise unsuitable, but it

probably would be sugRailroad Location Survey

gestive of a practicable

route. After locating on What constitutes a location survey for a railroad?—R. S. D.

the map the best obtain

able line, it should then Much of the railroad location of the

be transferred to the country has been done by picking out

ground. Measure to the line on the ground, even making it

scale the lengths of all follow in places the backbone line of the

"tangents” (the straight preliminary survey, running from one

lines joining the curves), course to the next by means of suitable

and the radii and curves. In the hands of a good engi- lengths of all curves. Inneer, the method is not necessarily very

stead of scaling off the bad, but it is much improved by the fol

length of a curve, it may lowing modification:

be more accurate to The work of the preliminary survey is

measure with

procarefully plotted from the transit notes

tractor, or with a scale and cross-section book to a scale of 200

of chords, the angle befeet per inch. On this map may be

tween the tangents at plotted one or more trial location lines.

each end of the curve, Each of these consists of circular curves

and from the angle and joined by tangents. The location line

the radius compute the must pass through any predetermined

length. Usually the lopoints and yet join them by lines which

cated line will lie fairly will give the best location, considering

close to the preliminary the conflicting interests. Within the line-close enough limits of the preliminary map, several that tie lines may readily locations are generally possible; and one

be run between them. great element of the value of such a map

These should be scaled lies in the ease with which several routes

from the map. may be laid out and compared. Profiles

vent the accumulation of may be drawn for each line laid down, by

error due to inaccuranoting the intersection of the line with

cies, the length (or each contour. Drawing on the profile

radii) of curves or the the required grade line, will give a rela

length of tangents should tive idea of the amount of earthwork re- be altered if necessary so quired. The method is especially valua

as to make the location ble when "development" is necessary.


check on the ground Although such a line must sometimes

with the positions of the be laid out by a bold and apparently un- stakes of the preliminary systematic trial of a route, yet some ap

survey. proach to a systematic solution may be made as follows: Assume that the max

To Make a Ladder imum ruling grade has been determined

I wish to make a light, stout ladder for use as 1.2 per cent, and that the contours

in the orchard. I would prefer to construct have, as usual, a five-foot interval. It

one of material more durable than pine.will require 417 feet of 1.2 per cent grade T. H. E. to rise five feet. Set a pair of dividers Spruce and hickory would probably so that they will step off spaces of 417 make th best combination for your purfeet on the map. Starting on a contour pose. The wood should be thoroughly at the required beginning of a grade, seasoned, care being taken that no warp swing the dividers so that they will just appear while drying. This is particularly



To pre


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