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encederst difficul soft beloormation Maies

hired to advance pressure has been force

Tunneling Shield sect the transverse bulkheads and floor

platforms, and with them divide the THE illustration shows one of the enor- cross-section of the shield into as many

mous shields used in tunneling un- as nine separate chambers. der the East River, at New York, in The miners work in front of the foroperation. The course of the subway lies ward bulkhead. The material excavated through a geological formation hard is shoveled up, and deposited in inclined above and very soft below, so that the chutes passing through both diaphragms greatest difficulty has been experi- of the shield and delivering to the rear, enced in driving the shield on grade. whence it is shoveled into dump carts. It has passed through mud, quick One shield requires 50 men to operate sand, solid rock, and sand. A force it. They work two three-hour shifts of 4,000 tons' pressure has been re- daily, owing to the exhausting effects of quired to advance it. In order to reduce the air-pressure, so that 200 men are the heavy pneumatic pressure as far as required in one day for one shield. The possible, the grade of the tunnel was air-pressure to which the men are exkept as close to the bed of the river as posed of course is slight compared with considerations of safety would allow that which forces the shield forward. Between the roof of the subway and the The former is to keep back the water, river bottom, but eight feet of soil and which otherwise would flood the tunnel. rock intervene. However, clay has been deposited till the roof is from 15 to 25 feet high.

This shield has a diameter of 23 ft. 61/2 in., a length of 18 ft. 6 in., and weighs 542,000 pounds. The outside cylindrical shell is composed of three thicknesses of 34-inch plates. It is reinforced in the rear with an additional plate threeeighths of an inch in thickness; and in front the vertical edge is reinforced with a segmental cast-steel cutting edge.

Near the center of the shield are two vertical, transverse bulkheads, which, with girdles and braces, support two working platforms. Two vertical bulkheads inter





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great bridges across the East River at pension shows wide gaps that have been New York.

made; while the immense steel crossFor several years past, magazines and beams have pressed against the hangers newspapers have been filled with descrip- below them to such an extent that it has tions of what is called the Williamsburg been necessary to cut notches in the crossBridge, owing to the mammoth size of beams to prevent them from breaking the this structure and the engineering feats hangers. Careful measurements made involved in its erection. In round num- with gauges specially designed for the bers, the bridge is said to have cost fully purpose, show that the center span of the 20 million dollars. While it was being bridge has actually moved more than built, a very singular accident occurred three feet from its original position. This to it by reason of a fire which started span alone weighs 7,000 tons, and this among some inflammable material used enormous load is at the present time for covering the cables. Before it was pressing against the anchorage on the checked, the fire spread to the temporary Williamsburg side. woodwork used in the construction, con- Shortly after the fire, it was supposed sumed most of this, and then burned that all of the wires in the cables which away much of the covering of the cables. had been badly damaged had been reThe greatest damage done, however, was placed; but evidently the heat affected the cables and other parts of the structure to a greater extent than was thought to be the case. Some of the most noted bridge engineers and constructors in the world have been called to make an examination of the structure, but are at a loss to know what to do to prevent it from further shifting. Owing to the great strain upon the cables caused by the movement, it is impossible to use the bridge except for ordinary traffic, and no railroad cars of any kind are allowed to cross it, as it is feared the vibration and weight might cause a portion of the bridge to collapse utterly.—HENRY HALE.




Hospital on Wheels SHOWING How TELEPHONE Connection IS MADE THROUGH ON a siding in the Southern Pacific

Railway's great freight yards at San gate the resident" surgeon estimates that Francisco, stands an old worn-out and not less than 600 men and women of all weather-beaten Pullman tourist coach, conditions of life were treated in this old "Number 2,500.” How many times this rolling emergency hospital. The patients old car has crossed the continent, or how were brought in for only temporary remany hundreds of thousands of miles it lief, and later sent to the various large has traveled, no one knows. Some time improvised hospitals for permanent treatago the old car was condemned, placed on ment. “the retired list," and left standing on an unused siding. But this car has an interesting history, replete with human suf

Phoning from Trains fering. .

TELEPHONES on the fast limited At the time of the fell disaster to San I trains enable the traveler to comFrancisco, and for many weeks following municate with his family and confer with the calamity, this car did most valiant his business associates, up to the instant service for the cause of afflicted human of the train's departure from the station. ity. Immediately after the shock, this Frequently a passenger is still talking car was hastily converted into an emer- when the connecting plug is withdrawn gency hospital by the Railroad Company. and the cars begin to move. The few Operating tables, with a complete surgical and medical equipment, were quickly installed. A force of surgeons and several trained nurses were at once assigned for duty there. From all directions were brought the crippled and the maimed who were victims of the earth quake and fire. Even the dying were brought there, quietly to breathe their last. For weeks following the catastrophe the car was a

A Good Samaritan On Wheels. most busy scene both day


Rolling emergency hospital equipped by Southern Pacific Railway in San Francisco and night. In the aggre

after the earthquake.

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seconds, however, that might otherwise constructed in Berlin, Germany, and conbe lost in going from the telephone in tains a bath of metal salts or mixtures of the station to the coach, are often of the such, which are raised by the electric curmost vital importance. A package may rent to a liquid, incandescent condition. have been mislaid, an urgent message The furnace may be adjusted at will for may have to be delivered.

any temperature intermediary between

750° and 1,325° C.

The furnace comprises a rectangular tank of fireproof material, for receiving the salt baths, which is fitted into an iron casing lined with fire-resisting mortar. Single-phase current is supplied through wrought-iron electrodes fitted opposite one another. The electrical energy is converted to the low tension at which it is to be used, by a transformer connected to two iron rails communicating with the electrodes. The temperature is regulated by controlling the number of windings in the


As the metal salt is

non-conductive when The service is in the observation car cold, the process is started by heating and is in charge of the official stenogra- with the aid of a removable auxiliary pher of the train. The wiring is the electrode. same as for the ordinary telephone. As Whereas in ordinary hardening furthe train comes to a stand in the station, naces the rapid destruction of the crucia plug connection is made beneath the bles involves a rather high expense, the car, and all is ready for use.

consumption of wrought-iron electrodes, The illustration shows the manner in as occurring in the present furnace, is which the connecting wire runs from far less expensive. The samples are the train.

raised to the proper temperature in about one-fifth the time required in the case of

the gas furnace, thus securing a greatly Electric Annealing

increased output. W HILE ordinary annealing furnaces, The temperature required for the

designed for heating by gas or liardening of ordinary tool steel does not coal, do not permit of an accurate exceed 850° C., while figures intermeadjustment or maintenance of the diary between 1,000° and 1,150° C., or temperature appropriate to each given in certain cases even 1,300° C., will prove case, electricity has recently been necessary for the annealing of rapidfound a most suitable means of tool steel. Three standard types of furoperating such furnaces. A special ad- nace, designed for maximum tempervantage secured by inward heating is the atures of 850o, 1,150°, and 1,300° C., reuniformity of temperature, avoiding any spectively, are accordingly constructed. deformation, internal strain, etc., in the The results obtained by the electric procsamples treated. The type of furnace ess are said to be equally satisfactory with represented herewith has recently been those given by furnaces of the old type.



Largest Car-Ferry THE Solano, the big ferry that trans1 ports freight and passenger trains of the Southern Pacific Railroad Company across upper San Francisco Bay, is the largest ferry in the world. The ferry was built several years ago for the express purpose of transporting trains across the bay, as the channel at this point is too wide and deep to be bridged without great expense, or without interfering with water navigation. The ferry also makes a short cut across, saving much time over the old route of circling the bay.

Touring Car ABOUT TO Start in Race with AIRSHIP. The ferry runs into a slip prepared for it on either shore, and fits so snug, when ers of the marine type. It is a sidethe landing is made, that the tracks on wheeler, operated by walking-beam. land, and those on the boat, fit exactly end to end. The train on the boat runs ashore, and the one waiting rolls aboard.

Airship Races Auto As the ferry is over 400 feet long, a passenger train of five cars need not un THE unusual spectacle of a race becouple; but the long “overland” trains, - tween an automobile and an airship consisting of twelve and thirteen cars, are was recently witnessed in California. cut in the middle and drawn aboard in The course lay from Los Angeles to Potwo sections. To accommodate the rising mona, a distance of 35 miles. Bad roads, and falling of the tide, and to make the aggravated by large crowds, gave the track ends meet, there is a long apron, or Man Angel, as the aërial courser was approach, at each landing, which is raised called, something of a handicap. In spite or lowered by hydraulic power. The fer- of this fact, however, the automobile ry is propelled by an immense twin en- easily won, covering the distance in 1 gine, developing 600 horse-power, steam hour 35 minutes. The airship came to being supplied by a battery of four boil- earth five miles from where it started.

The coursetly, witnessed and an airship

crowds, bad roads,

hed, someth as the

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