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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.

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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 2: There would be no particular then be given a bath in dilute nitric or

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

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 of 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 I am handy with tools and like to make the

two parts sulphuric acid to one part things I use. Can you suggest how to con

nitric. A combination of the glycerin struct an indoor croquet set ?-M. W. N. with the acids at once takes place with

scum

or

cream is

measure

a

the result that

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 sug

gestive of a practicable Railroad Location Survey

route. After locating on What constitutes a location survey for a

the map the best obtainrailroad?—R. S. D.

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

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. To premay 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 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.

AN ORCHARD

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 the 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

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(or

LADDER,

true in the case of the pieces of spruce, dow stool S (Fig. 1). The loose end of which are to form the sides or uprights. the curtain (c) should be secured to the The holes for the rungs should be bored bottom rail of the sash (A). When the with a 15-16ths inch auger. The rungs window is raised, the curtain unrolls,

and the opening in the storm frame is automatically covered. In Fig. 2, D represents a strip which should be nailed in

the position indicated, to hold the curtain A

at the side. A sheet-metal cover B is for the purpose of protecting the roller. If one prefers, the upper instead of the

lower half of the window may be fitted C

in this way.

B

S

Condensed Steam as Feed Water What danger arises from using the condensed steam from a surface condenser as feed water for the boiler.-A. H. O.

When the condensed steam from a surface condenser is used as feed water for the boiler, there is danger from cylinder oil entering the boiler with the condensed steam. Oil separators extract nearly all the oil, but it will accumulate

Fig 1. WINDOW FIXTURE FOR VENTILATION WITHOUT

DRAUGHT.
Sectional view.

very fast.

themselves should be turned from hick

If oil enters the boiler, the resulting ory, or, as a substitute, from tough white

conditions will vary with the nature of oak, and the ends brought to shape by the oil. Animal oil is more destructive means of a hollow l-inch auger. The

than mineral. Mineral oil in small quanvarious parts are then ready to be joined tities under ordinary conditions, does not together. If it is desired to work among

seem to cause serious effects; when dense branches, the pieces of spruce, in

present in large quantities, it accumulates drying, may be brought to the shape indi

at the lowest point in the boiler, or coats cated in the drawing. A hook at top,

the entire inside. In the case of animal adds to the safety of the ladder.

oil, it accumulates in a solid mass at the lowest point of the boiler. This mass

is a very poor heat conductor and preVentilating a Bedroom

vents transmission of heat from the boiler Can you suggest some system of adequately plates or tubes, causing overheating at ventilating a bedroom without draught?-T. A. J.

this point. The section will then yield The following method is said to have

under the boiler pressure, and cause bag

ging or possible rupture. given satisfaction. A regulation storm window sash from which the lower panes have been removed, is put in place. Instead of the panes, some stout cloth is used. It is better, ordinarily, to use some А flowered cloth, say silk or cotton, as such material gives a pleasing effect. With the inside window open, no draught will be felt.

A mcre permanent system may be installed as follows: Take an ordinary curtain roll, and remove the little dogs that hold the cloth from unwinding. The curtain itself should be of unsized ma

Fig. 2. WINDOW FIXTURE FOR VENTILATION WITHOUT terial. Fasten the roller R to the win

D

C

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DRAUGHT,

Photographing Blue Prints through the electrotype, into the negative Can blue-prints be photographed success-, plate. The grids may not be in contact; fully?-N. H.

connections between the plates may be The following method of photograph- broken ; the electrolyte may be too strong ing blue-prints is said to have produced or too weak; a short circuit may have good results: Bleach the print in dilute been formed by the active materials dropaqua ammonia, and then immerse in a ping out of the grid and accumulating in weak solution of tannic acid. This latter the bottom of the jar; or a coating of may be mixed by dissolving a heaping non-conducting material

may

have teaspoonful of dry tannic acid powder in formed on the particles of the active maa glass of water. The drawing will stand terial. out in nonactinic red; a photograph of same will give a negative having black lines on clear glass. Backed with white

Making Gravel Roofing paper, this can be used for copy in the How is gravel roofing made ?-T. H. J. photo-engraving process.

The surface of the roof is first covered

Demagnetizing a Watch
Will you suggest a way to demagnetize a
watch?-H. F. F.
The watch should be set securely be-

notches "deep fore one of the poles of an electro-mag

#14 copper wire net of high power. Before the turning on of the current, which should be done gradually, the watch should be rapidly revolved, though this is not necessary if an alternating current is used. Either a laminated case, or none at all, must be

METHOD OF ADJUSTING CROSS-BAR FOR TABLE-Rack. used, in this event. At the end of some 12 or 15 seconds, the watch may be re

with dry felt paper. Upon this are next moved.

laid several layers, from three to five, of

tarred felt. The various layers should Rack Beneath Table

lap over the seams, so as to make all

snug and tight. Where walls and chimI should like to place beneath a rough working table an adjustable rack that could be

neys intervene, the felt should be turned easily removed.-T. J. R.

up four or six inches and nailed to the The accompanying drawing shows obstruction, strips of wood first being very clearly, a serviceable and cheap laid over the felt. method of making such a rack. Saw notches 18 inch deep in the legs of the table, and with the use of wire, the cross

Cementing Old Shingles bars may be held in place. Loose boards

Can old shingles be covered with cement. may then be placed across, and quickly

satisfactorily?-L. T. M. removed, if the occasion should require.

It would hardly be worth while to The rack may be raised or lowered to

make the experiment, as the results would the height desired, in an instant.

doubtless be unsatisfactory. The only

method, short of concrete shingles thein111-Working Accumulator

selves, is to cover the roof with expanded

metal laths. These should be bent up The accumulator of my electric runabout is unsatisfactory, the service being irregular. Can

well at the walls. Over these, lay a covyou suggest the cause of the trouble?-H. ering of concrete, about an inch in thickA. P.

ness. At best, however, this would There is probably some obstruction or serve but temporarily, and would not be resistance to the proper fow of current advisable treatment for a roof of any from the positive plate of the cell,

cell, value.

FOR PIPING HOUSE TANK.

House Tank on Roof

Process of Electrotyping Please print a drawing showing the proper

Please describe the process of electrotyping. way to make pipe connections for a house tank.

-G, P. Of what material is it best to construct An important application of electrosuch a tank?-J. D. G.

lysis is in electro-plating a portion of letThe accompanying illustration shows ter press,-a form or page,—for use in the ordinary type of tank that is used newspapers or books, and in copying enin private dwellings. With regard to gravings for printing from, instead of

using the original blocks.

The set-up type. must be carefully jusRelief Pipe Pump Pipe

tified and very firmly locked up, to with

stand the pressure used in making the Vent Pipe

wax impression.

First the forms are cleaned from printer's ink and dried, then brushed over with plumbago to prevent the wax from sticking. The molding composition, consisting of beeswax with five to twenty per cent turpentine, is poured into the molding case, and must present a smooth

even face, free from cracks and bubHouse Supply Emptying Pipe

bles. This surface is carefully and evenly brushed with plumbago and polished and into it the face of the type is forced by a hydraulic or toggle press. The mold is

then carefully removed and built up or location, the tank should be at least ten corrected by the addition of wax, where feet above the level of the highest fixture necessary. to be supplied. Formerly lead lined The mold is now plumbagoed and all wooden tanks were extensively used and excess of plumbago removed by a brush in some places are still. But carbonates

or bellows. Copper wire conductors are or sulphates of lead are liable to be dis

now embedded in the mold, which is then solved from the lining, with deleterious made the cathode in a saturated solution results to the human system. Of course, of copper sulphate acidulated with sulif the tank is merely used to store soft phuric acid. Large copper anodes keep water for bathing purposes, this is im- the liquid stocked with the metal. material, Iron tanks are perhaps more Copper is deposited evenly on the sursatisfactory, on the whole.

face of the mold, to about the thickness of good book paper, or heavier, according to the use to which it will be put. When

a sufficiently thick layer has been obCoal vs. Water Gas

tained, the mold is taken from the bath,

and the wax removed by pouring hot Is danger of asphyxiation greater from water

water over the surface of the copper, gas than from illuminating coal gas ?-A. D. E.

which may then be gently stripped off. Chemists agree that inhalation of il- A solution of caustic potash removes the luminating coal gas in small quantities is film of wax from the copper shell, which dangerous neither to life nor health, has now to be backed up with stereotype though continued exposure may result in metal. After washing the cavity of the chronic poisoning, owing to the presence shell with a solution of zinc chloride, it of a small percentage of carbon monox- is warmed and coated thinly with tinner's ide. Water gas contains a much larger solder, and then melted stereotype metal proportion of this carbon monoxide. is poured in to make a layer about oneHence a state of unconsciousness is very eighth of an inch thick. This will withquickly induced by the inhalation of wa- stand the pressure of the printing. The ter gas. One per cent of this gas in air is plate is then carefully corrected by a fatal.

finisher and mounted on a block of wood.

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