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5. No twist or disturbance should occur in the water jet, in order that the greatest possible amount of power may be developed from the moving water (Fig. 4).

The demonstrations showed that the regulation of any water wheel is necessarily at the expense of efficiency. In most cases it is accomplished by throttling the water by means of a gate, which materially reduces the working pressure. The needle nozzle (Fig. 5) is a device which accomplishes the desired result with the least loss in pressure and velocity, and is consequently highly efficient. It consists of a conical shaped tip in which is inserted a concentric tapered plug or needle, generally similar in shape to a "plumb-bob." A change of position of this plug causes a corresponding change of discharge area in the nozzle. The amount of water used is thus varied, and the power of the wheel proportionately influenced.

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Trains Lighted by Turbines

By F. Peterson

HE accompanying illustration shows a 15-kilowatt Curtis steam turbine and electrical generator, mounted on top of a locomotive in service on

the Pennsylvania Railroad. This small direct-connected unit is utilized for train lighting, and its combination of small size with relatively large output is possible because of the high speed of the little prime mover.

This equipment includes an 80-volt direct-current electrical generator of the two-pole type, driven at a speed of 4,000 revolutions per minute by a Curtis steam turbine constructed at Schenectady, N. Y., by the General Electric Company. The entire turbine and generator weigh only 1,850 pounds, and supply current not only for general train lighting, but also for the operation of the locomotive headlight.

These train-lighting sets are also constructed of 20-kilowatt and 25-kilowatt capacity, operating at a speed of 3,600 revolutions per minute, and supplying

continuous current at 125 volts. The turbines are supplied with steam at from 80 to 200 pounds' pressure, the exhaust passing into the atmosphere, no condensers being employed.

The steam-turbine train-lighting unit, as shown, occupies but small space, the area being 22 inches by 66 inches. In order to protect the same from the weather, sheet-iron casings surrounding both the turbine and the generator are provided, which not only reduce the condensation losses, but protect the generator and turbine from moisture and dirt.

The exhaust is carried into the stack when the train-lighting set is mounted on the locomotive; and when mounted in the baggage car, the steam is obtained from the locomotive by a flexible steam hose and coupling.

The separate steam dynamo unit is more generally favored for electric trainlighting, not only on account of its simplicity of operation and electrical connections, but also on account of its reliability. Electrical generators driven by the axles of the cars are in satisfactory oper

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TURBINE AND DYNAMO MOUNTED ON PENNSYLVANIA RAILWAY LOCOMOTIVE FOR ELECTRIC

TRAIN-LIGHTING SERVICE.

Turbine is of Curtis type (steam), and dynamo of 15-K. W. capacity.

ation both in this country and in Europe; but storage batteries are absolutely essential; and, in fact, with any system of train lighting, even with the separate steam-turbine generator, the accumulator plant is essential.

The Leitner-Lucas train-lighting system utilizes automatic regulating and switching devices in connection with the electrical generators, lamps, and storage batteries, when starting the voltage between the positive and negative terminals of the battery excites the field of the electrical generator, assisting the current from the main brushes, the field building up rapidly. The current from the armature increases; and the current instead of being supplied from the storage battery as the automatic switches come into action, is obtained from the electrical generator, not only lighting the lamps, but

also charging the storage cells. A small coil is in series with the lamps, which is energized as soon as the load is switched on, and its effect is to render the field excitation more positive, though it is not absolutely required.

Another automatic device employed is used for switching in the battery when the train comes to a stop. With the system using a separate dynamo driven from the car axle in connection with the storage battery, each railway coach has its own independent plant, including dynamo, battery, and switchboard, with automatic regulating apparatus.

With the turbo-generator outfit on the locomotive shown in the accompanying illustration the entire electrical equipment is compact and of light weight, and compares favorably in economy as well as reliability.

What Ancient Cannon Were Like

T

By Dr. Alfred Gradenwitz

Berlin Correspondent, TECHNICAL WORLD MAGAZINE

HE ancient Greek and Roman catapults, in construction so mystifying to military engineers for many centuries, have finally been reproduced. For this, credit is due Lieutenant Schramm of the German Army.

ANCIENT GREEK HAND-BOW. Called a "Gastraphetes," tension being obtained by pressing the body against curved back end of handle.

By painstaking and scientific research into the works of the military writers of both nations, he has been able to reconstruct models of the ancient weapons. His creations have partly been donated to national museums; the remainder have been sent to the Kaiser, for Saalburg Castle.

Greek ordnance-which was adopted by the Romans without any material alteration-was, almost without exception, dependent on the hand-bow principle. On trying to shoot a larger bullet to greater distances, the elastic arms of the bow were necessarily made so strong as to be no longer susceptible of tightening by hand. A tension shaft had therefore to be fitted to the bow, which shaft was tightened with levers or handwheels. Finally, as the power of bows. altogether failed to ensure the efficiency desired, their bending elasticity was replaced by the tensional elasticity of neura, that is, ropes made from animal sinews, woman's hair, or, in an emergency, horsehair. One of the accompanying illustrations represents three

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ANCIENT GREEK TYPES OF ORDNANCE, RECONSTRUCTED. 1-Euthytonon, for projecting arrows. 2-Palintonon, for projecting stone bullets at an inclination of about 40 degrees. 3-Onager, only weapon based on stick-catapult principle, projected stone or lead bullets in a steep arc with only one projecting arm.

types of the catapult. The figure on the left projects arrows; the one in the center, stone bullets at an inclination of

about 40 degrees; the one at the right, stone or lead bullets in a steep arc, with only one projecting arm.

Handling Mail by Machinery

By Max A. R. Brunner

HE displacement of human labor by machinery develops more and more every year. We now see work done by mechanical means which for centuries had been done by hand and which did not seem suitable for machinery. The new

Chicago Postoffice is a unique example of a new attempt to replace the human hand by machines. The basement and the first and second floors are filled with so many mechanical appliances that these places make the impression of a busy working factory rather than a government postoffice.

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MAIL-HANDLING MACHINERY IN CHICAGO POSTOFFICE. At left is belt-conveyor; and at right are drop-chutes, with scales, for mail-bags.

The accompanying photographs show two views of these belts and conveyors for mail bags. Along the east front of the large building are 14 heavy metal boxes standing on the sidewalk, which,

INCLINED CONVEYOR FOR MAIL-BAGS AND DROP-LETTERS.

as very few people know, are the doorway to the mechanical equipment underneath. These boxes open over chutes down which the mail wagon drivers throw their filled bags. At the inclined bottom of these chutes are two-ton weigh-hoppers, to discharge the mail upon tables. In the first picture, it can be seen that the front hopper has the doors closed; while the second and fourth have their doors opened to allow the mail-bags to fall upon the wooden table in front. The doors have a counterweight which swings around, and the weight of the bags is each time accurately recorded and filed in the postoffice, this record forming the basis of the cost for handling the mail matter. The sacks are then placed by hand upon the continuously moving large belt which runs along the chutes under the sidewalk. The belt is not of the trough-type, but is flat; and it moves. between wooden sills which are stationary and which serve to keep the sacks upon the belt. At the end of this belt in the background, the mail-bags are discharged automatically upon an inclined conveyor of the type shown in the second picture, and then pass to numerous

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