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that the copper deposited has attained sufficient thickness, the mould should be removed from the sulphate of copper solution, the wire detached from the dry cell, and the mould washed for some time in a stream of running water; after which it should be slung up by its wire to dry thoroughly in a warm place. When the work is quite dry, the binding wire is untwisted, and the wire carefully unwound from round the edge of the work. If the copper deposit is very thick at these points it will be advisable to file it down cautiously all round, so as to avoid breaking away any of the copper deposited on the front. Having thus filed awav any copper that may have extended round the edges of the work, the front of the mould should be held for a few seconds before a clear fire so as to warm the copper coating. This will cause it to expand slightly, after which, by cautiously pushing with the fingers from the back of the mould, the copper coating or "electrotype” can easily be detached. It may then be washed and brushed up with a soft nail-brush and soap and water, dried and mounted on velvet; or it may be "bronzed" with blacklead, or lacquered, if it is desired to preserve the beautiful surface it presents when first detached from the mould. The work or mould, if soiled with blacklead, may be cleaned with a soft tooth-brush moistened with benzine. It may be necessary after this to brush up with soap and water, using a fresh, clean brush.

Facsimile Duplicates When it is desired to produce a facsimile of the article to be copied, a trifling

modification must be made in the manipulation. This consists essentially in preparing, first, a wax mould or cast from the original, from which mould the copper electrotype is produced. To this end, take a strip of paper long enough to make four or five turns round the sides of the object to be copied. This must be bound round the edge so as to extend up above the face of the work to a height of nearly half an inch, and tied tightly round the sides. The whole should now be laid on a flat table, face upwards. Sufficient good beeswax to cover the face of the work to a depth of about 3/8 in. is now melted in a perfectly clean pipkin or ladle. The surface of the work and the inside of the paper binder are now heavily breathed upon, so as to prevent the wax adhering, when the melted wax is immediately poured in to a depth, as we have said, of about 38 in. The mould should now be allowed to stand for an hour or two to set and harden thoroughly. The paper binder is then removed, the wax mould pulled off, three or four turns of No. 20 wire bound round the edge, and the surface and edge of the mould carefully blackleaded with a very soft camel-hair brush. It will not be advisable to wet the blacklead ; but, using fine powder, breathing on the mould will suffice to render the surface sufficiently adhesive to take a goo:1 polish. The blackleaded mould is now to be treated precisely as recommended for the reversed facsimile. In the accompanying diagram are shown sectionally the proper position and connections of dry cell, wire to anode, depositing dish, mould, and wire from mould to negative pole of cell.

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work was found to have been not even discolored-in fact it was apparently entirely unharmed. A facing of pressed brick is being substituted for most of the terra-cotta, but some of the latter will still be used on the lower stories. All of the floors must also be replaced.

The total damage to this structure was estimated at between 35 and 40 per cent of its entire cost. The photographs show it immediately after the fire (side view), and after the facing was removed and the brick work begun (front view).

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MONSTER CIRCULAR DERRICK.

A UNIQUE TELEGRAPH STATION.

The first established in the "fire zone' at Balti ore

after the recent conflagration.

is known as a circular derrick, and is operated entirely by electric power. It has actually raised a weight of over 150 tons, swinging it around a circle 147 feet in diameter. Loads weighing seventy tons have been lifted and swung in a circle of 207 feet. The derrick will lift the heaviest cannon to a heiglit of 100 feet above the surface of the water, and yet its machinery is so simple that but two men are required to operate it.

This derrick is composed of a steel tower or framework carried on pile foundations. This tower, which is circular, is fitted with a track for the rollers that carry the movable or revolving portion of the derrick. The revolving portion consists of a heavily framed structure, circular in general form, and carry

tended along the trunk of a fallen telegraph pole, and messages were sent from this novel telegraph station to the metropolis. This was the first office opened in the business district after the disaster. The accompanying photograph shows an operator sending a message.

ing a movable jib from the outer end of which the several hoisting blocks descend vertically. The revolving portion of the derrick carries all the motors and machinery required for the various movements, as well as the balancing weights required to offset the tilting tendency of the jib. The revolution of the derrick is effected by means of two pinions,

Dangers of Imperfect Insulation
THE USE of electrical apparatus

is so prevalent that, as is well
known, a large number of fires

originate from the electric current. Investigations made by insurance men prove that much of the so-called insulation intended to protect inflammable material from the action of the electric current is so poor that it affords little or no protection, while some of the currents are of such voltage that ordinary insulation is no safeguard whatever. The accompanying photographs give an idea of the destruction caused by inadequate electrical work. The first photograph shows a number of fuse cut-outs which were placed on a 500-volt circuit. These were constructed with a porcelain base, but the insulation was not sufficient to prevent the current from communicating with wiring and woodwork about the cut-outs, with the result that a fire ensued which caused a loss of $25,000. While investigating the cause of the fire, the ex

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which engage with a circular rack fixed to the stationary tower or framework. Each of these pinions is driven by a General Electric motor, capable of developing 20 horse-power. The racking movement of the jib is effected by means of wire ropes leading over sheaves at the top of the jib, and wound on large drums, which are located in the revolving structure of the derrick. The inner and lower end of the jib has a pin connection to the revolving structure, so that, by winding up to the drum, the outer end is raised and is brought in toward the center, while unwinding the drum lowers the outer end and moves it out from the center. The hoisting blocks are carried, as before mentioned, from the outer end of the jib; and the leads from these blocks run down the jib to drums, which, like the others, are operated by electric motors.

Fuse Cut-Ours, 500-VOLT Circuit.

Showing Results of Defective Insulation. perts found the cut-outs in the condition shown in the picture, and sought no further to trace the origin of the trouble.

The second picture shows the way in which insulated wire will become defective. In this case not only was the

wire exposed to the weather, being on the outside of a building, but some one had thoughtlessly or maliciously cut through the insulation with a knife. The wire conveyed a powerful electric current for

of brick 450 feet long, 186 feet wide, and three stories high. Rising from the center of the structure are four chimney shafts, each 275 feet high, said to be the tallest in Europe. Their huge diameter

SIOWING HOW INSULATED WIRE WILL BECOME DEFECTIVE.

lighting. Leaking through the insulation where it had worn away, and through the cut, the current destroyed an office building in Buffalo, New York, causing a loss of about $60,000. The damaged part of the wire could have been replaced at an actual cost of less than $1, and the fire thereby averted, had the wiring been inspected properly. The photographs were taken by insurance inspectors who investigated the causes of the fires.—D. A. W.

is one of the wonders of London. They are 19 feet across at the top, and are ascended from the interior by means of iron “dogs” let into the brick work.

T he building is divided lengthwise into two portions. On the side nearest the

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Yerkes Builds World's Greatest

Power Plant
N AMERICAN — Charles T.

Yerkes—is building for the city
of London the greatest power

plant in the world. It is now nearing completion, and in less than a year will be driving trains all over the city. The plant is being erected on the south of the Thames, near Chelsea, and is to supply electricity to the District Railway, the Baker Street & Waterloo line, and the Great Northern, Brompton & Piccadiily Railway. For emergency purposes it will also be connected with

CHARLES T. Yerkes. the “Tube” from Shepherd's Bush and Mansion House and with the Metropoli- river are to be found the 64 great Babtan District Railway.

cock & Wilcox boilers. They are laid in The plant will be about twice the size two tiers, and the floor above is occupied of that at Niagara, and will cost over by the coal bunkers. The furnaces are $10,000,000. The building is a rectangle supplied with mechanical stokers, and the

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