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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).

A Unique Telegraph Office

O

NE RESULT of the recent great fire in Baltimore was to burn all of the telegraph offices in the busiest part of the city. It was supposed. that all of the wires extending to this section were also disconnected by the fire effects; but on the day after the conflagration, an electrician, making tests, found one wire which connected with New York City. A set of instruments was immediately secured. The wire ex

A UNIQUE TELEGRAPH STATION.

The first established in the "fire zone" at Baltix.ore

after the recent conflagration.

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

operator sending a message.

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MONSTER CIRCULAR DERRICK.

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 height 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

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LIFTING MACHINE IN OPERATION.

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.

T

Dangers of Imperfect Insulation HE 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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FUSE CUT-OUTS, 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

SHOWING HOW INSULATED WIRE WILL BECOME DEFECTIVE.

lighting. Leaking through the insula tion 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.

Yerkes Builds World's Greatest Power Plant

A

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 & Piccadilly Railway. For emergency purposes it will also be connected with the "Tube" from Shepherd's Bush and Mansion House and with the Metropolitan District Railway.

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The plant will be about twice the size of that at Niagara, and will cost over $10,000,000. The building is a rectangle

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

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.

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

CHARLES T. YERKES.

river are to be found the 64 great Babcock & Wilcox boilers. They are laid in two tiers, and the floor above is occupied by the coal bunkers. The furnaces are supplied with mechanical stokers, and the

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steam from the boilers will be superheated. The boilers represent about 1,200 horse-power each.

In the north side of the building are the turbine and generator sets. There will be eight turbines working eight generator sets in all, and space will be left for two more to be put in later. They have a capacity of 5,000 kilowatts each, and are by far the most powerful in En

Proposed Endless Street-Car

gland. These 40,000 kilowatts, together A CONTINUOUS TRAIN OF

with an auxiliary plant for condensers. and exciter sets, will represent in all in driving power some 600,000 horse-power. The electric pressure at the station will be 11,000 volts, alternating current, which will be subdued by rotary converters and transformers to 400 volts, direct current, at the different substations.

SEATS on a moving sidewalk has been suggested as the method of solving the transportation problem of New York and Chicago. The device is something of an endless street-car which the passenger can enter anywhere he desires. It is proposed to use the system in New York in connecting the Manhattan terminals of the three great bridges over the East River with one another, and with the subway and elevated railroads, as well as with the principal surface lines running north and south. The moving seats are simply an improvement on the moving sidewalks and continuous trains of the Chicago World's Fair and Paris Exposition. Two "stepping" platforms run alongside the train platform. The first moves at a rate of about three miles

The enormous stators in the generating sets weigh 50 tons each. All were built by the Westinghouse Company. Four were made at Pittsburg and four at Trafford Park, Manchester. Inside the stators, motors revolve at a tremendous pace, and the current is collected on three slip rings. Above the turbine level are switchboard galleries for high tension, and at the east end of the turbine level similar galleries for "exciter" sets and station lighting and for low-tension stators and motors.

In the construction nearly 20,000 tons of steel have been used. The foundations have been sunk to 40 feet below the land level, and consist of brick lying on concrete, which in its turn lies on the blue clay.

Outside the building is a large basin constructed beside the river especially for barges bringing coal to the station. The basin accommodates eight of these barges. A temporary conveyor will carry the coal from the barges to the great conveyor built of laced steel against the main building, which will take the coal to the bunkers in the roof of the station. By means of these same conveyors, all ashes will be taken back to other barges. Close by the docks are water filters in brick towers, their object being to treat the water used and thus prevent "furring" of boilers.

Mr. Yerkes is a Chicagoan, and it was in Chicago that he received his schooling

in municipal railway affairs. He built most of the Chicago street-car lines, and he is adopting the same system of avoiding congestion of traffic in London which he so successfully employed in the western metropolis.

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pere, under tensions ranging between 20,000 and 25,000 volts, at an angular speed ranging between 600 and 700 revolutions, is excited by means of a small exciting machine mounted on the end of the shaft and supplying current at a tension of I 10 volts.

The problem solved in connection with both these machines was a rather difficult one, as the highest tensions so far obtained with continuous current hardly attained 10,000 volts.

The latter machine, as pictured herewith, is a bipolar dynamo resembling ex

ternally a modern radial pole alternator. The inductor, being made of laminated

iron,

rotates in the interior of a ring con

sisting of two pieces and constituting the armature; the latter, accordingly, is fixed. The armature coils, numbering 48, are fitted into an equal number of slots in ring, being insulated by means of a

the

metallic brushes, sliding in the interior of its surface. In order to avoid any risk of arcs being produced between the segments of the collector on account of the

high-potential difference between each two of them (500 volts as an average), a small blowing device has been provided, mounted at the end of the shaft of the

pulley controlling the exciting machine. By means of two nozzles directed towards the brushes, strong air currents are made to blow out any arcs produced between the segments. As, however, with any higher intensity, there would still be a risk of short circuits, a condenser was branched off in shunt between each plate of the collector; this arrangement, which has given most satisfactory results, was patented by the company.

The exciting current, as above said, is supplied by a small dynamo as in the case of an ordinary alternator; this

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