en knew how to control the wonderful power of electricity. They did not know what electricity is, nor do we know to-day, thoug

ssible to build great factories wherever a supply of water for the boilers could be obtained. Cities were built around the factories. Cities already great became greater. With the

eriod the great industries which characterize our modern civilization, and which arose out of the discoveries that science had made in the centuries preceding, attained a high degree of development. In this chapter we shal

ic Bat

he zinc and copper plates are placed in sulphuric acid diluted with water. As the acid eats the zinc, hydrogen gas is formed. This gas collects in bubbles on the copper plate and weakens the current. The aim of inventors wa

ox. This tube dipped into the other liquid. The hydrogen gas, as it was formed by the acid acting on the zinc, could go through the walls of the tube, but was stopped by the copper sulphate, and copper was deposited on the copper plate. This copper deposit in no way interfered with the current, so that the current was not weakened until the

–A DANI

e kept separate by gravity, the heavy copper sulphate being at the bottom. The gravity cell has until recently been extensively used in telegraphy, and continues in use in short-di

–A GRAV

ry Ba

named. There can be no battery without a liquid. In the dry battery the zinc cup forming the outside of the cell is one of the plates of the cell (Fig. 39). The battery appears to be dry because the solution of sal ammoniac is absorbed by blotting-paper or other porous substance in contact with the zinc. The inner pla

NG WHAT IS IN

ell circuit is open nearly all the time, the current flowing only while the button is being pressed. Some forms of wet battery work in the same way as the dry battery, and are used like-wise for open-circuit work. In these batteries carbon and

orage

Daniell cells or dry cells. In a short time one of the lead strips will be found covered with a red coating. The surface of this lead strip is no longer lead but an oxide of lead, somewhat like the rust that forms on iron. If th

This roughened the surface of the lead plates, so that the battery would hold a greater charge. The battery was then charged by passing a current through it in one direction only for a considerable length of time. Feeble cells were used for charging. It took days, and sometimes weeks, to charge the

making up the battery. Later it was found that the battery would hold a still greater charge if the plates were made in the form of "grids" (Fig. 40), and the cavities filled with the active material-the negative with spongy lea

GE BATTERY, SHO

ATTERY PLATE MADE F

is no longer a battery, though it may be made one again by passing a current through it in the opposite direction from that which it gives out. In this it differs from the voltaic batt

By reducing the weight of the battery which the machine must carry the weight of the truck may also be reduced. In the Edison battery the positive plates are made of a grid of

r, and more successful in operation. Two hundred and fifty automobiles were equipped with it, and it proved superior to lead batteries for this purpose. But it was not to Edison's liking. He threw the machinery, worth thousands o

Dy

was about four inches in length and yielded a brilliant light, but as the cost was six dollars a minute it was not thought practical. Attempts were made

m burning coal or falling water? For answer man looked to the great discovery of Faraday and his "new electrical machine." Inventors in

nce telegraphy and in electroplating to-day the dynamo is used. Without the dynamo, electric lighting, electric power, and electric traction as developed in the ni

netized than steel, and found that the strength of an electromagnet can be greatly increased by making the core of a soft-iron rod and bending the rod into the form of a horseshoe (Fig. 42).

URGEON'S E

wire that had been used by Sturgeon. Fig. 43 shows such a magnet. One of Henry's magnets weighed fifty-nine and a half pounds, and would hold up a ton of iron. Sturgeon said: "Professor Henry has produced a

AGNET WITH MANY TUR

OMAGNET LIFTING T

aking the circuit in another coil wound on the same iron core. A current was induced in a metal disk by revolving it between the poles of a magnet. In every case there was motion in a magnetic field, or the field itself was changed. A changing

rseshoe magnet are shown in Fig. 36), because they indicate the direction in which the magnet pulls a piece of iron-that is, the direction of the magnetic force. Now, if a current is to be induced in a wire, the wire must move across the lines of force. If the wire moves alo

d them with some success in producing lights for lighthouses, but the defects of these machines were so great that the lighti

ns' D

d, but the electromagnet received its current from another machine in which a steel magnet was used. Siemens found that the steel magnet could be dispensed with, and that a coil turning between the poles of an electromagnet could furnish the current for the electromagnet. Two things are needed, then, to make a dynamo: an electromagnet and a coil to turn between the poles of that magnet. The rotating coil, which usually contains a soft-iron core, is called the "armature." The coil will furnish current for the magnet and s

AMO WITH SIEM

g of the iron core of the armature, caused by the action of induced currents. There are induced currents in the iron core as well as in the coil, and, for the same reason, the coil and the iron co

alian, Pacinotti. Gramme applied the principle discovered by Siemens to Pacinotti's ring, and produced the first practical dynamo for strong currents. Th

–RING A

NAMO PATENTED IN

e used for ki

by C

rum A

her and by air-spaces within the core. The insulation prevents the small currents from flowing around in the core. The air-spaces serve for cooling. The drum armature was a great improvement over both the Siemens and the Gramme armatures. With the Siemens one-coil armature there is a point in each revolution at which there is no current. The current, therefore, varies during each revolution of the armature from zero to full strength. In

, SHOWING HOW AN ARMATU

ompound-Wo

the dynamo on the shaft of the engine. He also used more powerful field-magnets than had been used before. His greatest improvement, however, was in making the dynamo self-regulating, so that the dynamo will send out the strength of current that is needed. Such a dynamo will send out more current when more lights are turned on. Whether it supplies curren

s of the field-magnet. There is only one circuit. The same current flows through the coils of the magnet and through the outer circuit, which may contain lights or motors. Such a dyna

SERIES-W

es through the line wire for use in lights or motors. This is called the "shunt winding" (Fig. 50). The shunt-wound dynamo is used for incandescen

SHUNT-WO

was first used by Edison, is a combina

COMPOUND-W

of electric current with the flow of water. Open a water-faucet and notice how fast the water flows. Then open several other faucets connected with the same water-pipe. Probably the water will not flow so fast from the first faucet. That is because the pressure has been lowered by the flow of water from the other faucets. If we could make the water adjust its own pressure and keep the pressure always the same, then the water would always flow at the same rate through a faucet, no matter how many other faucets were opened. This is what happen

OF EDISON'S

iation of Edison Il

OUNTED ON THE TRUC

ights in the car. When the train is not running

tric

ll be the age of electricity. Before the end of the nineteenth century, however, electr

nd that electric currents attract or repel each other, and this because of their magnetic action. Faraday found that one pole of a magnet will spin round a wire through which a

produced. If a current is sent through the coils, the armature turns and does work. If the machine is used to supply an electric current, it is a dynamo. If used to do work-as, for example, to propel a street-car and for that purpose receives a current-it is a motor. The same machine may be used for either purpose. In practice there are some differences in the winding of the coils of dynamos and motors, yet any dynamo can be used as a motor and any motor can be used as a dynamo. This discovery made it possible to transmit power to a distance with little wa

t Electr

ctical electric locomotive, the invention of Doctor Siemens. The locomotive and its passenger-coach were absurdly small. The track was circular, and about one thousand feet in length. This diminutive

ST ELECTRIC

ery Hall was used to run the other as a motor and so propel the car. The rails served to conduct the current. A third rail in the middle of the track was connected to one pole of the dynamo and the two

. Edison employed no trolley line or third rail, but only the two rails of the track as conductors, sending the current out through one rail and back through t

an 5 per cent. Edison found that he could realize in his motor 70 per cent. of the power applied to the dynamo, whereas the German inventor was able to realize only 60 per cent. The improvement was largely d

EDISON ELECT

otor as it was starting, and so prevent the burning-out of the armature coils. The locomotive was started with the resistance-boxes in circuit, and after gaining some speed the operator would plug the various boxes out of circuit, and in that way increase the speed. When the motor is running there is a back-pressure, or a pressure that would cause a current to flow in the opposite direction from that which is running the motor. Because of this back-pressure the current which actually flows through the motor is small, and the resistance-boxes may be safely taken out of the circuit. Finding the

'S FIRST PASSE

raffic, not for profit, but that Germany might have the honor of building the first practical electric railway. The line was built between Berlin and Lichterfelde, a distance of about one and a half miles. A horse-car seating twenty-six persons was pressed into service. A motor was mounted between the axles, and a central-station dynamo exactly like

COMMERCIAL E

converted into

ric L

hen the rapid growth of railways and commerce brought about a rapid growth of cities, and with the growth of cities the need of illuminatio

ss than a millionth part of the air remained. They little dreamed that there was any connection between the high vacuum and the problem of lighting. Discoverers were at

ight-watchman, only to yield the greater por

aim of inventors to produce a continuous spark that should give out a brilliant light. It was thought for a time that the electric battery would solve th

flows through something which resists its flow, heat is produced. The high resistance of the air-gap causes such intense heat that the tips of the carbons become white hot and give out a brilliant light. If examined

t supplied with current by the Gramme machine. In the same year the Brush system of arc lig

uld furnish enough light for a number of houses if the light could be divided so that there might be just the right amount of light in each room. But t

ent. At the end of two days he succeeded in getting a perfect filament, but when he attempted to seal it in the glass bulb it broke. He patiently worked another day, and was rewarded by securing a good carbon filament, sealed in a glass globe. He pumped the air out of this globe, sealed it, and sent a current through the carbon thread. He tried a weak current at first. There was a faint glow. He increased the current. The thread glowed more brightly. He continued to increase the current until the slender thread of carbon, which would crumble at a touch, was carrying a current that would melt a wire of platinum strong enough to support a weight of several pounds. The carbon gave a bright light. He had found a means of causing the electric current to furnish a large number of small lights. Fig. 58 is an excellent photograph of Edison at work in his laboratory. Fig. 59 shows some of Edison's first incandescent lamps. He next set out in search of the best kind of carbon for the purpose. He carbonized paper and wood of various kinds-in fact, everything he could find that would yield a carbo

'S GREATEST INVENTOR, A

1904, by

OUS HORSESHOE PAPER-

904, by Will

CTRIC-LIGHTING PLANT; INSTALLED ON

urn in a fraction of a second. The carbon must be in a vacuum, and so the air is pumped out of the light bulb with a special kind of air-pump invented not long before Ediso

r of kinds of incandescent light have been devised, using different kinds of filaments and adapted to a variety of uses.

d the light is given out from the tips of the white-hot carbons. In the mercury vapor light the light is given out from the mercury vapo

Tele

ic action of an electric current was discovered. When Oersted's discovery was made known men began to think of signalling to a distance by means of the action of an electric current on a magnetic needle. A current may be sent over a very long wire, and it will deflect a magnetic needle at the other end. The movements of the needle may be controlled by opening and closing the circuit, and a system of signals or an alphabet may be arranged. A number of needle telegraphs were invented, but they were too slow in action. Two other great inventions w

ntion of the wireless telegraph. Nothing could be known of its movements until it returned. The need of a telegraph was keenly felt in America when the new republic was extended to the Pacific Coast. An English statesman said, after the United States acquired Cali

, with its coils of many turns of insulated wire, was needed for long-distance signalling. In one of the rooms of the Albany Academy, Professor Henry caused an electromagnet to sound a bell when the current was transmitted through

nts of Ampère, which he had witnessed while in Europe, and, in reply to a question, said that electricity passes instantaneously over any known length of wire. The thought of transmitting words by mea

food. Receiving an appointment as professor in the University of the City of New York, he moved to one of the buildings of that university

his pupils describes hi

patronage. I paid my fifty dollars; that settled one quarter's tuition. I remember, when the second was du

my boy, how are

ay I have been disappointed; but

ated, sadly; 'I shall

ad,

ad by sta

ed. I said, hurriedly: 'Would

save my life; that i

d, and the two dined together. It was

e and broken by means of a key at the other end of the line. In Morse's first instrument (Fig. 62) the armature carried a pen, which was drawn across a ribbon of paper when the armature was attracted by the magnet. If the pen was held by the magnet for a very short time, a dot was made; if for a longer time, a dash. The pen was soon discarded, and the message taken by sound only. The Morse alphabet now in use was d

TELEGRAP

S FIRST TELEGR

lead type shown in the lower right-hand corner was used in making electrical contact when sending a message. Th

by C

ize the coils of the relay and cause the armature to close another circuit. This second circuit includes the sounder and a battery in the same station as the sounder, which we shall call "the local battery." The relay simply acts as a contact key, and closes the circuit of the local battery. Thus the current from the local battery flows through the sounder and produces a lo

PHIC CIRCUIT WITH

. It is necessary, therefore, to make a ground connection at each end of the line, the instruments being connected between the line wire and th

MPLE TELEGRA

en one key is to be used the switch at that station mu

light are the same. A telegraphic signal would go more than seven times around the earth in one sec

but the inventor did not despair. A bill for an appropriation to establish a telegraphic line between Washington and Baltimore passed the House by a small majority. The last day of the session came. Ten o'clock at night, two hours before adjournment, and the Senate had not acted. A senator advised Morse to go home and think no more of it, saying that the Senate was not in

dollars appropriated for the telegraph. Being the first to bring the news of his success, Mr. Morse promised her that the first message over t

ination for the Vice-Presidency, which had been tendered him. The convention refused to accept a message sent by telegraph, and sent a committee to Washingto

RAPH INSTRUMENT USE

by C

ater, and prevent the escape of the electric current. Just when it was needed such a substance was discovered. In 1843, when Morse was working on his telegraph, it was found that the juice of a certain kind of tree growing in the Malayan Archipelago formed a substance somewhat like rubber but more durable, and especially suited t

x Tel

one wire do the work of two was accomplished by the invention of the duplex system. In duplex telegraphy two messages may be sent

es are so arranged that the currents flowing through them are equal, the relay will not be magnetized, because one current would tend to make the end A a north pole, and the other current would tend to make the same end a south pole. The result is that the relay coil is not ma

GES ARE SENT OVER ONE

the line, no current will flow through the sounder. But if a current comes over the line from the distant station this current divides at D, and a part goes through the sounder, causing it to click. The sounder is not affected, therefore, by the current from the home ba

RE SENT OVER ONE WIRE AT T

of which four messages may be transmitted over one wire at the same time. The first quadruplex system was invented by Edison in 1874, and in four years it saved

Tele

y a string, the end of the string being fastened to the middle of the stretched membrane. The sound of the voice causes this membrane to vibrate. As the membrane moves rapidly back and forth, it pulls and releases the string, and so causes the membrane at the other end to vibrate and give out the sound. This is the actual carrying of the sound vibrations along the string.) In the telephone it

as the magnet in the telegraph receiver pulls and releases the soft-iron armature as the circuit is made and broken. The thin membrane caused to vibrate in this way would give out the sound. A telephone on this principle was invented by Philip Reis, a schoolmaster in Germany. The transmitter was carved out of wood in the shape of a human ear, the t

ce. His plan was to cause the ear itself to trace on smoked glass the waves produced by the different letters of the alphabet, and to use these tracings in teaching the deaf. Accordingly, a human ear was mounted on a suitable support, the stirrup-bone removed, le

ssages by means of musical sounds. In this telegraph he was using an electromagnet in the transmitter and another electromagnet in the receiver. He attached the soft-iron armature of each electromagnet to a stretched membrane of gold-beaters' skin, expecting that the sound of his voice would cause the membrane of the transmitter t

L TELEPHONE RECEI

cord can be seen on the end of the transmitter and of the receiver. An electromagnet is also shown over each membrane.

is professional work and finally giving it up, that he might give his whole time to his invention. He was forced to endure poverty and ridicule. He was called "a crank who says he can talk through a wire." Men said his invention could never be made

grows weaker, the magnet becomes weaker and does not pull so hard on the disk. The disk then springs back from the magnet. If these changes take place rapidly the disk moves back and forth rapidly and gives out a sound. The sound of the voice at the other end of the line sets the disk in the mouthpiece vibrat

TELEPHON

the iron disk. Now we have found that whenever a coil of wire is in a changing magnetic field a current is induced in the coil. The small coil in the transmitter, therefore, has a current induced in it. We have also found that when the magnetic field is made stronger the induced current flows in one direction, and when the field is made weaker the current flows in the opposite direction. Since the field in the transmitter is made alternately stronger and weaker, the current in the coil flows first in one direction, then in th

IVERS USED AS A

changes. When the carbons are pressed together more closely the current is stronger. When the pressure is less the current is weaker. We have, then, a varying current through the carbons. This current flows through the primary coil of an induction-coil, the secondary being connected to the line-wire. Now a curren

his there are many granules of carbon, so that instead of two carbon-poi

RBON-DUST

eiver a distance of one foot, if changed into an alternating current, would be sufficient to keep up a sound in the receiver for a hundred thousand years. Because of its extreme sensitiveness the telephone requires a complete wire circ

saction, while the telephone left no sign. There was a time when men feared to trust each other, but now large business deals are made by telephone; products of the farm, the factory, a

Phon

when the vibrations of the disk caused a fine steel point to pierce one of his fingers held just behind the disk. This set him to thinking. If the sound of his voice could cause the disk to vibrate with force enough to pierce the skin, would

linder must move forward as it turns, so that its path will be a spiral. If, now, the stylus is placed at the starting-point and the cylinder turned rapidly the stylus will move rapidly up and down as it goes over the indentations in the cylinder, and so cause the metal disk to vibrate and give out a sound like that received at first. In the earliest phonographs the cylinder was covered with

OGRAPH, A FORERUNNE

RST PHONOGRAPH AND

by C

-En

he power in each case is obtained by explosion-in the cannon the explosion of powder, in the engine the explosion of a mixture of air and gas. Powder-engines with pistons were propo

l gas-engine. He used gas distilled from wood, coal, or oil. The gas, mixed with the proper proportion of air, was introduced into a tank which he called

number of years, for this engineer had proposed to compress the mixture of gas and air before fi

in 1860. From this time to the end of the century the gas-engine developed r

e, engine. This engine is called four-cycle because the piston makes four strokes for every explosion. There is one stroke to admit the mixture of gas and air to the cylinder, another to compress the gas and air, at the

E. GAS AND AIR ADMI

OKE. MIXTURE OF GA

XTURE IS EXPLODED AND EXPAND

THE BURNED-OUT MIXTURE OF GAS AN

-CYCLE G

on is that the steam-engine wastes its heat. Heat is given to the condenser, to the iron of the boiler, to the connecting pipes and the air around them, while in the gas-engine the heat is produced in the cylinder by the explosion and the power applied directly to the piston-head. More than this, a steam-engine when at rest wastes heat; there must be a fire under the boiler if the engine is to be ready for use on

opposite side of the piston. At the end of this stroke the compressed mixture is exploded, and power is applied to the piston during about one-fourth of the next stroke. During the remainder of the second stroke the burned-out gas escapes, and the fresh mixtur

E. CRANK AND CONNECTING-ROD

inder, but the gas-engine requires to be turned until at least one explosion takes pl

le one cylinder is on the power stroke the next is on the compression stroke, the third on the admission stroke, and the fourth on the exh

ON BUGGY." FORERUNNER O

eam Lo

ine. In the Newcomen engine, you will remember, it was the pressure of air, not the pressure of steam, that lifted the weight. Evans soon set about building an engine in which the pressure of steam should do the work. He is sometimes called the "Watt of America," for he did in America much the same work that Watt did in Scotland. Evans built the first successful non-condensing engine-that is, an engine in which the steam, af

his engines, the "Rocket," possessed all the elements of the modern locomotive. He combined in the "Rocket" the

ys for hauling coal by means of horses over iron tracks, and other locomotives that travelled over an ordinary road; but this was the first roa

ME EARLY L

right is Stephe

by C

to secure an act of Parliament. Stephenson was compelled to undergo a severe cross-examination by a committee of Parliam

that would stand a speed

es

he

our. I mean to say that if it would bear the weight

require a stronger railway to carry th

seen persons go over, and they know that it would bear them better at a greater velocity

mply that the roa

I mean to mak

o convince the committee, however, and secure the act of Parliament was more difficult than to build the

ocomoti

ot with a narrow bottom. The greater the heating-surface-that is, the greater the surface of heated metal in contact with the water-the more quickly the water will boil and the more quickly steam can be produced. In a locomotive the aim is to use as large a heating-surface as possible. This is done by making the fire-box double and allowing the water to circulate in the space between the inn

so be seen that the valve closes the admission-port, and so cuts off the steam before the piston has made a full stroke. The steam that is shut up in the cylinder continues to expand and act on the piston. At the same time the valve opens the exhaust-port, allowing the steam to escape from the other side of the piston; but it closes this port before the piston has quite finished the stroke. The small quantity of steam thus shut up acts like a cushion to prevent the piston st

W A LOCOMO

ow the course

steam may be sum

ed to the cylin

es admission-

inder expands, acting on th

-port to allow used st

ear. The throttle-valve is at the entrance to the steam-pipe in the steam-do

locomotive would move forward, but if the valve is changed so as to admit steam to the left of the piston while the connecting-rod is in the position shown then the engine will move backward. Thus the direction can be controlled by the engineer in the cab. Of course, this can be done while the engine is in motion. The forward rod and the backward rod are each moved by an eccentric on the axle of the front driving-wheel. The two eccentrics are in opposite positions on the axle. An eccentric acts just like a crank, causing the rod to move forward and backward as the axle turns, and of course this motion is g

to the driving-wheels at points which are at right angles with each other, so that when the crank on one side is at the end of a stroke-

eam expands from one cylinder into another. The second cylinder must be larger in diameter than the first. In the triple expansion-engine the steam expands f

Tu

water-turbine and the steam-turbine work in very much the same way, the difference being due to the fact that steam expands as it drives the e

ke the lawn-sprinkler. As the water rushes out of the opening it pushes against the air. It cannot push against the air without pushing back at the same time. Never yet has any person or object in nature been able to push in one direction only. It cannot be done. If you push a cart forward you push backward against the ground at the same time. If there

–HERO'S

heel. It would have no power to move a second wheel. In this way he used practically all the power of the water. To save the power of the water by making all of the water strike the wheel at high speed the channel was made narrow just above the wheel, forming a mill-race. This applies to the undershot wheel. In the overshot wheel (Fig. 84) the power depends on the weight of the water and on its height. The water runs into buckets attached to the wheel, and, as it falls in these buckets, turns the wheel. The undershot wheel and the mill-race represent a common form of turbine, that form in which the steam or the water is forced in a jet against a set of curved blades. Fig. 85 shows a steam-turbine run by a jet of steam. In the water-tu

HOT WATER-WHEEL W

OVERSHOT

LAVAL STE

of steam strik

-TURBINE WITH TOP CASI

M OF TURBINE S

ow the course

T RUNS A DYNAMO GENERATING

through the large

the giant ships, defied the patrol-boats whose duty it was to keep out intruders, and raced down the lines of battle-ships at the then unheard-of speed of thirty-five knots an h

ver a number of rows of curved blades. The Parsons turbine is used on the fastest ocean liners. The Lusitania, one of the fastest stea

rives the air instead of being driven by it. The blades of the windmill and the electric fan are shaped very much like the screw propeller. The screw propeller, driven by an engine, would drive the water back if the ship were firmly anchored, just as the fan drives the air. But it cannot drive the water back without pushing forward on the s

The old paddle-wheels, with low-pressure engines, developed only about two horse-power for each ton of machinery. The turbine, with the twin-screw propeller, develops from six to seven horse-power for every ton of machinery. The modern steamer, wi