The Project Gutenberg eBook ofAppletons' Popular Science Monthly, February 1900

The Project Gutenberg eBook ofAppletons' Popular Science Monthly, February 1900This ebook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this ebook or online atwww.gutenberg.org. If you are not located in the United States, you will have to check the laws of the country where you are located before using this eBook.Title: Appletons' Popular Science Monthly, February 1900Author: VariousEditor: William Jay YoumansRelease date: October 23, 2014 [eBook #47181]Most recently updated: October 24, 2024Language: EnglishCredits: Produced by Greg Bergquist, Charlie Howard, and the OnlineDistributed Proofreading Team at http://www.pgdp.net (Thisfile was produced from images generously made availableby The Internet Archive)*** START OF THE PROJECT GUTENBERG EBOOK APPLETONS' POPULAR SCIENCE MONTHLY, FEBRUARY 1900 ***

This ebook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this ebook or online atwww.gutenberg.org. If you are not located in the United States, you will have to check the laws of the country where you are located before using this eBook.

Title: Appletons' Popular Science Monthly, February 1900Author: VariousEditor: William Jay YoumansRelease date: October 23, 2014 [eBook #47181]Most recently updated: October 24, 2024Language: EnglishCredits: Produced by Greg Bergquist, Charlie Howard, and the OnlineDistributed Proofreading Team at http://www.pgdp.net (Thisfile was produced from images generously made availableby The Internet Archive)

Title: Appletons' Popular Science Monthly, February 1900

Author: VariousEditor: William Jay Youmans

Author: Various

Editor: William Jay Youmans

Release date: October 23, 2014 [eBook #47181]Most recently updated: October 24, 2024

Language: English

Credits: Produced by Greg Bergquist, Charlie Howard, and the OnlineDistributed Proofreading Team at http://www.pgdp.net (Thisfile was produced from images generously made availableby The Internet Archive)

*** START OF THE PROJECT GUTENBERG EBOOK APPLETONS' POPULAR SCIENCE MONTHLY, FEBRUARY 1900 ***

Transcriber’s note: Table of Contents added by Transcriber.

Established by Edward L. Youmans

EDITED BYWILLIAM JAY YOUMANS

VOL. LVINOVEMBER, 1899, TO APRIL, 1900

NEW YORKD. APPLETON AND COMPANY1900

FEBRUARY, 1900.

Theadvances in science lead to hopes of the sudden accumulation of gold, just as the discovery of new worlds led our ancestors to invest in many inflated enterprises of commerce and conquest. This older temptation has passed away, for there are no new worlds to discover, and this small globe has been practically staked out; but the mysterious domains of science are still illimitable, and afford vast opportunities for inflated schemes which have their prototype in the South Sea Bubble.

Let us refresh our memory of this surprising delusion. It arose in the reign of Queen Anne, nearly one hundred and eighty years ago, and when we consider the extent of the speculation and gambling which it caused and the number of those who lost everything and who consigned their families to bitter poverty, we are tempted to class it with those other calamities which preceded it and which afflicted England so heavily—the great fire of London and the plague. The South Sea Company claimed to have enormous sources of profit in certain exclusive privileges, obtained from the Spanish Government, for trading in their possessions in South America and Mexico; and it may be well for us in these times of the flotation of schemes for obtaining gold from salt water and from sands, of power from air and something more ethereal than air, to be reminded of the many bubbles that came into existence and burst at the time of the collapse of the South Sea Bubble.

The stock of the South Sea Company rose from one hundred to a thousand, and an army of future victims crowded the offices ofthe company, anxious to invest in what they believed would suddenly enrich them. Indeed, all England seemed to go mad, and the craze of the time is reflected in the writings of Pope and Swift. Pope says:

“At length corruption like a general floodDid deluge all; and avarice creeping on,Spread like a low-born mist, and hid the sun.Statesmen and patriots plied alike the stocks,Peeress and butler shared alike the box;And judges jobbed, and bishops bit the town,And mighty dukes packed cards for half a crown;Britain was sunk in lucre’s sordid charms.”

The rise of the great bubble was accompanied by the formation of hundreds of minor ones. Among these we will mention a few which are pertinent to the subject of this paper:

A wheel for perpetual motion. Capital, one million pounds.

For extracting silver from lead.

For the transmutation of quicksilver into a malleable fine metal.

Puckles Machine Company, for discharging round and square cannon balls and bullets, and making a total revolution in “the art of war.”

For carrying on an undertaking of great advantage, “but nobody to know what it is.”

It is estimated that the proposed capital for floating these and similar schemes was three hundred million pounds. We find, in the annals of the time, that the Duchess of Marlborough persuaded her husband, John Churchill, the great general, not to increase his holdings, and to sell his shares; he, like a sensible man, took a sensible woman’s advice and made one hundred thousand pounds. When we come to speak of the connection of women with modern delusions, we must remember this act of one of their sex.

At this time, nearly two hundred years after the singular outbreak of chimerical projects of Queen Anne’s reign, we can match some of these bubbles almost exactly; for have we not had the Keeley motor, the extraction of gold from salt water, and is there not great activity in making the wonder of the public over some advance in science a source of money-making? The unscientific person is certainly open to a new danger in the increasing tendency to promote enterprises based upon some new scientific discovery, and it behooves the followers of science to suggest a remedy for this growing evil. I shall endeavor to do my part in this paper in pointing out the necessity of some oracular medium—a scientific oracle of Delphos—to which the common man can repair and get trustworthy information, for it is a melancholy fact that such informationcan not be obtained from the daily press or from the literary magazines of the time.

Many of our newspapers draw such an income from their advertising columns that the editors are unwilling to print any criticism which would lead to the restriction of this source of gain; thus if a company promoting a scientific bubble should advertise liberally in a leading newspaper, the editors are usually loath to insert an article upon the scheme, for the printing of the criticism might lead to the withdrawal of the advertisement. It is possible that the editors of such daily papers have not overmuch confidence in the judgment of scientific men, for have not the latter often been mistaken? There was Lardner, who prophesied that steamships could not cross the Atlantic, but we must remember that Lardner was not a scientific man; he was a popularizer of science, and never made a scientific investigation. It is said that there have been college professors who have denied the possibility of sending messages under the ocean. This I also doubt, for I am a witness in the flesh of the way such stories can arise. Not long since I was invited to speak before a commercial club, and the presiding officer, in introducing me, remarked: “The professor will now address you on the advances in electricity. When I was in college I well remember his describing an electric motor and his remark that it would never become a practical invention.” There was, of course, laughter, and the president sat down with a comfortable air of having made a point. The professor pointed out that the presiding officer graduated before he became professor in the university, and before the Gramme machine and the electric motor were invented. Nevertheless, the world loves to believe in the inaccuracy of the accurate, and even a sophomore takes infinite delight in discovering arithmetical mistakes in an edition of Newton’sPrincipia.

I mention this proneness to believe that scientific men are apt to be mistaken, for it is a blame laid at their doors often by the promoters of scientific bubbles, and for a very easily understood reason, and the editors of newspapers and literary magazines can ease their consciences after publishing sensational scientific articles by reflecting on the fallibility of the followers of science. Lawyers and judges, too, make their mistakes; nevertheless, we continue to resort to them for advice; and few editors, I imagine, would dare to publish a legal opinion without consulting an authority in law. Yet we read every day so-called scientific articles in newspapers and magazines which have evidently never been submitted to competent critics. Have we not read statements of the possibility of exploding powder magazines on board ships by electric waves; of the manufacture of liquid air without the expenditure of energy;of electricity direct from coal; papers on the nebular theory, more nebulous than any nebula yet discovered? When we read a broad sheet in the morning paper setting forth a glowing scheme to manufacture power out of nothing, to what oracle can we repair to ascertain the truth? It is true that common sense might lead the reader to reflect that when he is told that the shares can now be obtained for five dollars, but in a short time they will be advanced to ten dollars, and now is the time to invest, that such good things are quickly taken up without the necessity of advertising. When the morning mail brings a prospectus of a company formed to make diamonds by electricity, a company with ten million dollars capital (why not one hundred millions?), to whom should one go to allay the fever of sudden gain? While men and women will carefully consider which line of steamships to Europe is the best equipped with engines, the efficiency of which depends upon the laws that prove the impossibility of perpetual motion, they enter at the same time upon schemes to obtain power without the consumption of work.

We are indeed confronted with the curious fact that even so-called intelligent people can be led to believe that what we have learned in regard to the working of Nature may be thrown aside, and that some new and unrelated laws may rule supreme. Thus we have what is called Christian Science, one of the intuitional sciences which may be said to add a new peril to matrimony. We find cultivated men believing that a government can make money by pronouncing silver equal to gold. Thus there are those who fondle their delusions and those who bank upon credulity. Education seems to be ineffectual with some temperaments; on the whole, however, it has a saving grace, and there are undoubtedly a number in the community who would welcome a source of scientific authority which might answer for them just as the Times does in political and economic questions to an Englishman. The American has especial reason to fear scientific bubbles, for our patent laws make it comparatively easy for promoters to make a great show of vested rights. One method is to build an imposing plant, with powerful dynamos and with a multiplicity of electrical devices, and to capitalize for an enormous sum an expensive plant in sight with millions in patents of very little value. The proposed investor is taken to see the great plant; its magnitude appeals to his reverence for size, and his pocketbook is soon at the service of the promoter. Another method is to select some scheme which is on the borderland between physics and chemistry, such as the electrolytic method of obtaining gold from salt water. There is a minute quantity of gold in salt water, and the chemist, thinkingthat electricity might afford an economical method of treating large quantities of water, is reticent in regard to such a scheme, while the electrician, ignorant of chemistry, is ready to concede that the chemists may have found a cheap extractor, so the promoter can play the chemist against the electrician, and there is no arbitrator in sight. The American is peculiarly in peril from the absence of a large body of men trained in technical science, such as exist in Germany. He also has been unduly excited, and his desire for love of sudden wealth stimulated by phenomenal successes. The commercial triumph of the telephone has led to a multitude of scientific bubbles, and has resulted, like the discovery of gold in the Klondike, in a rush into electrical schemes which have been held up to a hungry crowd of victims as second only to the Bell telephone.

While the telegraph and the telephone can prevent speculations like the South Sea Bubble in a great measure, for such schemes were much aided by a lack of a general dissemination of intelligence, and this lack is supplied by a quick interchange of knowledge, they bring their own peculiar peril, for they are examples of what profit may be reaped from discovery in the world of science. The commercial enterprises of the world have been brought within reach of the many by the telegraph and telephone. They no longer belong to the few, while the successful working of the field of science is still confined to a minority and the general public; even the cultivated people are very ignorant of the approaches to the New El Dorado. No bogus land scheme or salted mining enterprise can be kept in existence to-day for a long period; but the Keeley motor, with its ethereal vibrations and its pseudo-molecular motions, was limited in activity only by the life of the promoter. Instead of the alchemists we have the seekers after power, which costs nothing, and in the train of the honest inventor there are unscrupulous promoters ready to capitalize any remarkable new fact or discovery which attracts public attention.

I have mentioned the influence of the first Duchess of Marlborough in inducing her husband, the great duke, to sell out his shares in the South Sea Bubble when they had risen to a high value because this example of discrimination and prudence in a woman supports one in the belief that all women are not prone to invest in women’s bank schemes, in Keeley motors, or in enterprises for “carrying on an undertaking of great advantage, but nobody to know what it is.” One of my friends recently visited the office of a company which proposed to produce power without the expenditure of a due amount of energy, and found among those anxious to invest a woman who said that she had just received a dividend from the company for extracting gold from salt water, and she wasanxious to invest it in the new power company. The dividend was the result of a liquidation of the Gold from Sea Water Company, and represented half of her original sum. She had come out of one delusion with a loss of half of her property, and was now ready to enter another one with the remaining half. It was an old-fashioned notion that women should be kept in ignorance of business, for business knowledge, it was thought, was the concern of the husbands. This notion prevails still in some quarters, and there may be some connection between the number of women in Christian Science temples and their lack of education in practical matters, or in what may be called the legal business habit—a habit which weighs the probabilities of this and that, and leads to ways of exact thinking.

One of the remedies for this proneness of women to invest in scientific bubbles, to invest money on faith, is the lack of exact training, which is not acquired by them either in private schools or colleges. The classes of philosophy and psychology in women’s colleges are crowded, while those in the exact sciences have only handfuls. This remark also applies to the students in men’s colleges, and we realize in this respect how closely college women imitate college men. They follow the latter also in the habit of taking lecture courses, a custom which increases vagueness, inaccuracy of thought, and looseness of statement. This choice of studies by the young women in their colleges is a serious question for mankind, in view of the speculative spirit which the feminine sex show toward scientific bubbles and schemes which promise an inordinate rate of interest; for the graduates of these colleges will become teachers of youth, and if not teachers they have an influence upon the coming citizen during his formative period. As teachers they will far outnumber men teachers, and they are fast coming into competition with men also in the routine of business offices and in certain positions in commercial houses. In these activities they will need a balance of judgment, exactness of thought, and business habits. They should be given a sufficient knowledge of the elements of physical science to know that power can not be created from nothing, and that the great mass of our knowledge of mechanics and of the relation of electricity to mechanics can not be overturned by any new discovery. Whatever is discovered must be related to what has preceded it. This is a characteristic of a science, and this is what distinguishes it from a delusion—namely, the great body of related facts put upon a mechanical basis, so that any fact can be substantiated and any phenomenon repeated. When this latter test is applied to many of the isms of the day they fade into thin air, and young women need especially to be taught to apply sucha test. It would seem as if the present choice of study by women students tended to intensify vagueness of thought rather than to correct it, to keep them in ignorance of business habits rather than to educate them in the balance of judgment on economic questions.

Women are born speculators, and are peculiarly prone to invest money and heart in bubbles. Being the power behind the throne, they can carry men into action, and it seems to me that especial attention should be paid in women’s colleges to the studies that cultivate accurate thought and business methods. A certain amount of the study of scientific methods and a study of common law might take the place of the study of philosophy, psychology, and biology, certainly in the first years of a woman’s college course, for psychology and biology are studies which demand long scientific training and maturity of thought. Recently I heard the following conversation at a bank in Cambridge. The cashier was speaking with a young lady: “Miss ——, your friend has overdrawn her account three hundred dollars, and you say she has left Cambridge.” “Yes, the trouble with Jane is she is too much educated.” A long residence in a university town makes one wary of educational theories, but the proneness of women to invest in women’s banks and bogus trust companies certainly seems to need a corrective in a new college curriculum. Men can indulge in delusions and can recover mental balance, and perhaps their fortunes; but women are apt to become bankrupt permanently. Their experience in business delusions is similar to that in affairs of the heart. Washington Irving says of this feminine attribute:

“She sends forth her sympathies on adventure; she embarks her whole soul in the traffic of affection, and if shipwrecked her case is hopeless, for it is a bankruptcy of the heart.”

More mathematics and science, and less philosophy and psychology, might correct that vagueness of thought which leads both men and women into delusion.

Now for our other remedies. Shall we have an academy which shall issue storm warnings of scientific bubbles? I fear that the influence of academies is waning, and that the conviction that there are as many good men outside of the academy as inside would militate against their dicta. We could have courts of scientific appeal, with judges appointed by the State to sit on scientific questions of perplexity, and to sift expert opinions. Such a constitution of scientific courts might be a good thing in several ways—a saving health to the public. The college professor would certainly be greatly relieved of endeavors of promoters to use the name and reputation of the professor’s university, and incidentally the little his own name might add. This remedial solution is not in sight,and we must direct our vision in another direction. We know that the newspaper can not serve us, for we seek to kill sensations, and it seeks to live on them. We are bound to turn to some journal or periodical which will publish only what it considers sound science and will eschew sensational science; a journal which, just as the London Times is regarded as the authority on political and economical questions, will be looked up to as an authority on matters of science.

In order, therefore, to protect the public against scientific bubbles we must impress upon both men and women the fact that an education in science is desirable, and is becoming more important as the world grows older; but until a scientific education becomes more general, it is important that there should be some scientific oracle of Delphos, and I can not think of any better than a well-managed scientific journal, the editors of which will seek for the best information on scientific questions which interest the financial world. When it is known that such a journal admits to its pages nothing that is sensational, when it is realized that the best specialists contribute to it, surely it will become a saving help in times of trouble.

Note.—The illustrations of railway generator and switchboard were made from photographs kindly furnished by the Westinghouse Electric and Manufacturing Company.For the photographs of the electric truck and car controller we are indebted to the courtesy of the General Electric Company.

Note.—The illustrations of railway generator and switchboard were made from photographs kindly furnished by the Westinghouse Electric and Manufacturing Company.

For the photographs of the electric truck and car controller we are indebted to the courtesy of the General Electric Company.

Ifthe successful operation of a street-railway car by mechanical power depended wholly upon the ability to produce a motor of sufficient capacity to do the work, the problem would be an easy one to solve, and would have been solved long before the advent of the electric motor. Mere ability to furnish the necessary power, however, is not enough to meet the requirements. As already shown, the mechanism must be light, strong, compact, simple, and so well protected that it can not be injured except under abnormal conditions. In addition, speed-controlling devices must be provided whereby the velocity may be changed at will and in the shortest possible time, and with as nearly absolute precision as possible. This controlling mechanism must also be so arranged that the direction of motion may be varied with the greatest certainty and as rapidly as may at any time be required. The way in which theseresults are accomplished in an electrically operated car can be understood fromFigs. 18 and 19, which are line drawings, in a simplified form, of an ordinary trolley car.Fig. 18is an elevation showing the outline of the car body and the wheels in broken lines, while the motors and the wires through which the current is conveyed thereto are drawn in solid lines.Fig. 19is a plan in which the outline of the car floor and the platforms is represented in broken lines, the solid lines being the motors and connecting wires.

In almost every instance railway cars are provided with two motors, as shown atM Min these two figures. This arrangement is adopted not because one motor can not furnish all the power required, but simply for the purpose of making the equipment more reliable. Everything of human make is liable to fail; hence if only one motor were used there would be more or less liability of its giving out at a critical moment, and then the car would be helpless. If two motors are provided, should one give out the car would not be disabled, for the remaining machine would be able to run it to its destination. In order that this result may be successfully accomplished, each motor is made of sufficient capacity to run the car without being overtaxed, unless the load is abnormally large; but even under the latter conditions the machine will in ninety-nine cases out of a hundred withstand the strain. Some roads, in small towns, where the traffic is light and the expense must be kept down to the lowest point, use single-motor cars, so as to effect a saving in first cost. This course, however, is very seldom followed, except in places where there are no heavy grades or where there is very little probability of the loads becoming excessive, except at rare intervals. If the cars are provided with a single motor, when one becomes disabled from any cause it has to wait until overtaken by the car behind it, so that it may be pushed by the latter to the end of the road.

The electric current for operating the motors is generated in a power house that is located at some convenient point along the route. The current is conveyed to the moving cars by means of a trolley wire, which is markedTin the drawings. Unless the road is very small and operates but a few cars, this wire will not be sufficient to carry all the current, hence in most cases there are a number of supplementary wires, which are called feeders. These wires are carried along on poles, and at proper intervals are connected with the trolley wireT. The electric current passes from the trolley wire through the motors on the car, and thence to the railsR, and through these, and also through the ground, back to the power house. The exact path of the current is as follows:

Figs. 18, 19.—Outline Elevation and Plan of Electric Railway Car, showing Location of Motors, Controlling Switches, and Connecting Wires.

From the trolley wire, through the trolley polet, to the fixture on top of the car which holds the latter. From this fixture, as shown by the heavy full line, the current passes toa, which is a switch located under the car hood overhanging the platform. From this switch the current passes to a similar one, markedb, located in a like position at the other end of the car. These two switches are called emergency switches; they are provided simply as a safety device, and are used only when the main switches get out of order and the motorman can not turn the current off in the regular way. From the last hood switchbthe current passes tothe bottom of the car, where it enters the wired dat the pointc. This wired d, as will be seen, runs in both directions, and ends in the standsC C. These latter are the controlling switches, and are provided with a handleh, by means of which the current is turned on or off from the motors, and is directed through them in such a way as to make the car run in whichever direction may be desired. From the controllersC Cseveral wires are run under the car, as shown ate e e. These wires are generally bunched into one or two cables, but they are kept separate from each other by means of strong insulating coverings. Four wires lead into each motor, and three or four into each of the boxes markedG G. If the motors were required to run in one direction only, then two wires would be sufficient to convey the current to them; but as they have to run in either direction, at least three wires are necessary, but in almost every case four are used, as the results obtained thereby are more satisfactory. The boxesG Gare called rheostats, and are simply devices through which the current is run so as to reduce the speed of the car, and also for the purpose of graduating the strength of the current that passes through the motors in the act of starting. These rheostats are very seldom in use when the car is in motion, because it is a waste of power to pass the current through them. After the current has passed through the motors it enters the ironwork, and thus gets into the car wheels and finally to the track.

The lines drawn inFig. 18to indicate the position of the wires in the car do not show their actual position, but only the general direction they follow. From the trolley base to the first hood switch the wire, as a rule, is run along the car roof on one side of the ventilator, and the wire leading from the first to the second hood switch occupies a corresponding position on the opposite side of the roof. From the last hood switch,b, the wire is run down one corner of the car body, being either within the car body, or, if not, so covered by moldings as to not be reached by the hands of passengers. The wiresdandeare generally run under the car, and are firmly secured to it by means of suitable fastenings.

The controlling switchesC Care provided with one and sometimes two handles, one of which is used to regulate the speed of the car and stop and start it, while the other is for the purpose of reversing the direction in which it runs. The handlehis for the purpose of regulating the speed, and by means ofkthe direction of motion is changed. Beforehis moved from the inactive positionkis turned so that the car may run either forward or backward, as may be desired; then, whenhis moved, the car will start, and by varying the position ofhthe speed can be changed. If it is desiredto reverse the car,his brought back to the stop position,kis shifted to the reverse motion, and thenhis again turned to the running position. When the controlling switch is provided with only one handle this is turned in one direction to run the car ahead, and in the opposite direction to run it backward, the graduations in velocity being obtained by placing the handle in positions intermediate between the stop position and the highest speed position.

As will be noticed, the wired dbranches atcand runs in both directions. Now, when the controller handles are both turned to the stop position the current from the trolley can get no farther than the ends ofdin either switch, but if one of them is turned to the running position, the current at once passes to the wires in the cablee e e, and thus to the two motors. If the switchesC Care in proper working order and there is no disarrangement of the wires leading to the motors or those within the latter, the current will obey the movements of the handleh, but under other conditions it may not. If such an emergency arises, the motorman reaches up to the hood and turns the safety switchaorb, and thus cuts the current off.

The force with which the motors turn the car wheels around depends upon the strength of the current; this is owing to the fact that the magnetic force is increased or decreased by variations in the current strength. If the current is doubled the magnetic force of the armature is nearly doubled, and so is that of the field magnet, therefore the pull between the poles is nearly four times as great. From this it will be seen that the force with which the car is pushed ahead can be increased enormously by a comparatively small increase in the strength of the current. If the current strength is doubled, the propelling force is practically quadrupled; and if the current is increased four times, the propelling force is made nearly sixteen times as great.

The speed at which the car runs depends upon the force that impels the current through the wire, and which is called electro-motive force. The greater the electro-motive force, the higher the velocity. If the current passes from the wires in the cablee e ethrough each motor separately, and thence to the railsR, each machine will receive the effect of the whole electro-motive force of the current; but if after the current has passed through one motor it is directed through the other, then each machine will be acted upon by only one half the electro-motive force, and, as can be seen at once, the velocity in the first instance will be twice as great as in the last. This fact is taken advantage of in regulating the speed of the car, and controlling switches arranged so as to direct the current through the motors in this way are designatedas belonging to the series parallel type, the name being given from the fact that when the car is running slow, the current passes through the two motors in series—that is, through one after the other; but when the motors are running fast, a separate current passes through each machine.

Fig. 20.—View of Electric Railway Truck with One Motor on each Axle and provided with Magnetic Brakes.

If, when a car is running, the controlling switch is turned to cut the current off, the effect will be that the speed will gradually reduce; but if it is desired to effect a sudden stop, it becomes necessary to check the headway by means of a brake. For this purpose the hand brake ordinarily used on all types of cars is employed, but magnetic brakes are also used in some cases.Fig. 20shows a car truck equipped with two motors and magnetic brakes, one on each axle. Looking at the front end of the truck, the brake is seen on the left side of the axle, between the motor bearing and the car wheel. The larger drum, on the right side, is the casing within which the gear wheel and pinion are inclosed. These magnetic brakes are operated by a current generated by the motors, and not by that of the main line. As was explained in the first article, an electric motor can be made to act as a generator of electric current by simply reversing the direction in which the armature revolves. If we do not desire to reverse the direction of rotation, the result can still be attained by reversing the direction in whichthe current passes through the armature coils. It is evident that the direction of a car motor can not be reversed at the instant that it is desired to have it act as a generator—that is, when it is desired to put the brakes on; hence the direction of the current through the armature is reversed.

When a car is provided with magnetic brakes, the controlling switches are so made that when the handlehis moved back to the stop position it disconnects the motors from the trolley wire and at the same time connects them with the magnetic brakes in such a manner that they will act as generators and thus send current through the coils of the latter. In order that the force with which the brakes are applied may be graduated, the controlling switches are arranged so as to be moved several steps back of the point which in the ordinary type of switch would be the final stop position. When the handlehis placed on the first brake position the current generated by the motors is not very strong, and as a consequence the force of the brake is light, but sufficient to bring the car to a stop in a reasonable distance. If a quicker stop is desired the handle is moved to the second, third, or fourth brake position, thus increasing the retarding force as much as may be desired. Magnetic brakes are very desirable, as they save the car wheels, and furthermore afford an additional safety in cases where it is necessary to arrest the speed instantly.

The position of the motors with reference to the truck and car wheels is very well shown inFig. 20, and also the manner in which they are held in place. The covers of the openings through which access to the commutator brushes is obtained are removed from both motors, and in the forward one the top of the commutator and one of the brushes can be readily seen. The manner in which the motors are suspended from the truck is not the same in this figure as in those previously shown, but this is simply because the machines are not made by the same concern, and each manufacturer has his own design.

Fig. 21shows the appearance of the interior of the controlling switchesC C,Figs. 18 and 19. It will be noticed that there are two upright shafts, the ends of which project above the top of the box. The handlehis placed upon the shaft to the left, andkon that to the right. The first is the main controller, and the other is the reversing switch. It will be noticed that the main controller shaft carries a number of circular segments of different lengths; these are so disposed that they come in contact with suitable stationary pieces as the handlehis turned around, and thus vary the path of the current through the motors and the rheostats in the manner required to effect the desired changes in the velocityof the car. The reversing shaft is also provided with a number of segments, but these are not so easily seen, although they can be discerned on close examination. The wires from the cablee e eand also wired dare attached to the stationary pieces with which the segments carried by the two shafts make contact when the latter are moved around by the motorman. These wires can be seen back of the main switch shaft, and also above the board located at the lower left-hand corner. All these wires enter the controller through an opening in the bottom.

Fig. 21.—View of Interior of Car Controller.

In addition to the apparatus shown in Figs.18to21, electric cars are provided with a safety fuse and a lightning arrester, the object of the latter being to protect the motors from the destructive effects of lightning strokes. The object of the safety fuse is to protect the motor from injury when the current becomes too strong. An electric current in passing through a wire generates heat, and the stronger the current the greater the heat. If the wire is large and the current weak, the heat developed may be insufficient to raise the temperature to a noticeable degree; but, on the other hand, if the wire is small or the current very strong, the heat generated may be capable of raising the temperature of the metal to the fusing point. In fact, the incandescent lamp operates upon this principle; the carbon filament is traversed by a current of a strength sufficient to heat it to a point where it becomes intenselyluminous, and sometimes, through accident or otherwise, the current becomes strong enough to melt the filament, and then the light goes out. In an electric motor it is not necessary to raise the temperature of the wire to the melting point to do serious injury; in fact, if the heat is sufficient to char paper or cloth, the machine will be rendered useless until suitable repairs are made. The insulation of the wire coils is made principally of cotton, which is a very good electrical insulator in its natural state, but when carbonized by excessive heat it becomes a conductor. As soon as it becomes a conductor the current is no longer confined to the proper channel, but cuts through the insulation to find the shortest path through the machine. If safety fuses were not provided the danger of destroying the insulation of the motors and thus disabling the car would be decidedly great, for, as already said, the motors can not be stalled with an overload, the only effect produced being a reduction in the speed and an increase in current strength. Now, if there were no way of limiting the increase in current strength the motors, if greatly overloaded, would continue to operate until the insulation gave out. The safety fuse is simply a piece of wire of such size that it will be melted by a current that the motors can carry without being injured; hence when the current strength reaches a point where the safety of the apparatus is endangered the fuse melts and thus breaks the circuit and stops the further flow of current. Fuses are generally made of an alloy that melts at a low temperature, so that the molten metal may not set fire to anything upon which it may fall. These easily fused alloys are inferior to copper as electrical conductors, and on this account the fuse wire is as a rule much larger than that wound upon the motors, which fact makes its action somewhat mysterious to the uninitiated; but whatever its size may be, it is so proportioned that it will melt before the current rises to a strength that would injure the motor coils.

The manner in which the electric current generated in the power house reaches the motors is illustrated inFig. 22. In this figure four tracks are shown, which may be taken to represent roads running in as many different directions. The three squares at the left side represent generators located in the power house. The circlesa a arepresent switches, by means of which the generators are connected or disconnected from the trolley lines.AandBrepresent heavy metallic rods, generally made of copper, with which the generators are connected by means of the switchesa a a. These rods are called bus bars. The circlesb b b brepresent switches by means of which the current is turned on or off from the several tracks.

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