Chapter XIV: Some Recent Triumphs of Applied Science (6)

According to this theory, then, the electrical energy in evidence in the current from the voltaic cell, is drawn from a store of potential energy in the atoms of matter composing the liquid in the cell. In practice, as is well known, the liquid used is one that affects one of the metal poles more actively than the other, insuring vigorous chemical activity. But the principle of atomic and electrical dissociation just outlined is the one involved, according to theory, in every voltaic cell, whatever the particular combination of metals and liquids of which it is composed. It should be added, however, that while we are thus supplied with a thinkable explanation of the origin of this manifestation of electrical energy, no explanation is forthcoming, here any more than in the case of the dynamo, as to why the electrons rush off in a particular direction and thus establish an electrical current. Perhaps we should recall that the very existence of this current has at times been doubted. Quite recently, indeed, it has been held that the seeming current consists merely of a condition of strain or displacement of the ether. But we are here chiefly concerned with the electron theory, according to which, as we have all along noted, the seeming current is an actual current; the ether strain, if such exists, being due to the passage of the electrons.

PRACTICAL USES OF ELECTRICITY

Various effects of the current of electrons have been hinted at above. Considered in detail, the possible ways in which these currents may be utilized are multifarious. Yet, they may be all roughly classified into three divisions as follows:

First, cases in which the current of electricity is used to transmit energy from one place to another, and reproduce it in the form of molar motion. The dynamo, in its endless applications, illustrates one phase of such transportation of energy; and the call-bell, the telegraph, and the telephone represent another phase. In one case a relatively large quantity of electricity is necessary, in the other case a small quantity; but the principle involved--that of electric and magnetic induction--is the same in each.

The second method is that in which the current, generated by either a dynamo or a battery of voltaic cells, is made to encounter a relatively resistant medium in the course of its flow along the conducting circuit. Such resistance leads to the production of active vibrations among the particles of the resisting medium, producing the phenomena of heat and, if the activity is sufficient, the phenomena of light also. It will thus appear that in this class of cases, as in the other, there is an actual re-transformation of electrical energy into the energy of motion, only in this case the motion is that of molecules and not of larger bodies. The principle is utilized in the electrical heater, with which our electric street-cars are commonly provided, and which is making its way in the household for purposes of general heating and of cooking. It is utilized also in various factories, where the very high degree of heat attainable with the electrical furnace is employed to produce chemical dissociation and facilitate chemical combinations. By this means, for example, a compound of carbon and silicon, which is said to be the hardest known substance, except the diamond, is produced in commercial quantities. A familiar household illustration of the use of this principle is furnished by the electric light. The carbon filament in the electric bulb furnishes such resistance to the electric current that its particles are set violently aquiver. Under ordinary conditions the oxygen of the air would immediately unite with the carbon particles, volatilizing them, and thus instantly destroying the filament; but the vacuum bulb excludes the air, and thus gives relative permanency to the fragile thread.

The third class of cases in which the electric current is commercially utilized is that in which the transformations it effects are produced in solutions comparable to those of the voltaic cell, the principles involved being those pointed out in the earlier part of the present chapter. By this means a metal may be deposited in a pure state upon the surface of another metal made to act as a pole to the battery; as, for example, when forks, spoons, and other utensils of cheap metals are placed in a solution of a silver compound, and thus electroplated with silver. To produce the powerful effects necessary in the various commercial applications of this principle, the poles of the voltaic cell--which cell may become in practice a large tank--are connected with the current supplied by a dynamo. Various chemical plants at Niagara utilize portions of the currents from the great generators there in this way. Another familiar illustration of the principle is furnished by the copper electroplates from which most modern books are printed.

It appears, then, that all the multifarious uses of electricity in modern life are reducible to a few simple principles of action, just as electricity itself is reduced, according to the analysis of the modern physicist, to the activities of the elementary electron. There is nothing anomalous in this, however, for in the last analysis the mechanical principles involved in doing all the world's work are few and relatively simple, however ingenious and relatively complex may be the appliances through which these principles are made available.

IX

MAN'S NEWEST CO-LABORER: THE DYNAMO

As you stand waiting for your train at elevated or subway station you must have noticed the third rail. To outward appearance it is not different from the other rails. It seems a mere inert piece of steel. Yet you are well aware that a strange power abides there unseen--a power that pulls the train, and that lurks in hiding to strike a death-blow to any chance unfortunate whose foot or hand comes in contact with the rail. As the heavy train dashes up, dragged by this unseen power, probably you, in common with the rest of the world, have been led to remark, "Is it not marvelous?"

Marvelous it surely seems. Yet the cause of our astonishment is to be sought in the relative newness of the phenomena rather than in the nature of the phenomena themselves. At first glance it may seem that the intangible character of the electrical power gives it a unique claim on our wonderment. But a moment's reflection dispels this illusion. After all, electricity is no more intangible than heat. Neither the one nor the other can be seen or heard, but each alike may be felt. Yet we observe without astonishment a locomotive propelled by the power of heat--simply because the locomotive has become an old story. Again, electricity is far less intangible than gravitation. Not merely may electricity be felt, but it may be generated through transformation of other forms of energy; it may be stored away and measured; may be conducted at will through tortuous channels, or obstructed in its flight by the intervention of non-conductors. But gravitation submits to no such restrictions. It eludes all of our senses, and it absolutely disregards all barriers. To its catholic taste all substances are alike. It holds in bondage every particle of matter in the universe, and can enforce its influence over every kind of atom with an impartiality that is as astounding as it is inexorable. Moreover, this weird force, gravitation, has thus far evaded all man's efforts to classify or label it. No man has the slightest inkling as to what gravitation really is. If, as you glance at these lines, you should chance to release your hold and allow the volume to drop to the floor, you will have performed a miracle which no scientist in the world can even vaguely explain.

As regards our electric train, then, the fact that it stands there firmly, held fast to the rails by gravitation, is in reality as great and as inexplicable a marvel as the fact that the electric current gives it propulsion. Not only so, but the fact that the train goes forward of its own inertia, as we say, for a time after the current is shut off, presents to us yet another inexplicable marvel. It is a fundamental property of matter, we say, when once in motion to continue in motion until stopped by some counter-force; but that phrasing, expressive though it be of a fact upon which so many physical phenomena depend, is in no proper sense of the word an explanation.

Once for all, then, there is nothing unique, nothing preternaturally marvelous, about the phenomena of electricity. And indeed, it is interesting to note how quickly we become accustomed to these phenomena, and how little wonder they excite so soon as they cease to be novel. Even imaginative people have long since ceased to give thought to the trolley car; and within a week of the opening of New York's subway the average man came to regard it as much as a matter of course as if he had been accustomed to it from boyhood.

And yet, in another sense of the word, the electric motor is a wonderful contrivance. As an example of what man's ingenuity can accomplish toward transforming the powers of nature and adapting them to his own use, it is fully entitled to be called a marvel. Moreover, in the last analysis, we are as helpless to explain the nature of electricity as we are to explain the nature of gravitation. It is only the proximal phenomena of the electric current that can be explained. These phenomena, however, are full of interest. Let us examine them somewhat in detail, allowing them to lead us back from electric train to power-house and dynamo, and from dynamo as far toward the mystery of electric energy as present-day science can guide us.

THE MECHANISM OF THE DYNAMO

If we could look into the interior of a mechanism in connection with the trucks beneath the car, we should find an apparatus consisting essentially of coils of wire adjusted compactly about an axis, and closely fitted between the poles of a powerful electromagnet. These coils of wire constitute what is called an armature. When the current is switched on it passes through this armature, as well as through the electromagnet, and the mutual attractions and repulsions between the magnetic poles and the electric current in the coils of wire, cause the armature to revolve with such tremendous energy as to move the train--the motion of its axis being transmitted to the axle of the car-wheels by a simple gearing.

All this is simple enough if we regard only the _how_ and not the _why_ of the phenomena. Ignoring the _why_ for the moment, let us seek the origin of the current which, by being conducted through the armature, has produced the striking effect we have just witnessed. This current reaches the car through an overhead or underground wire. All that is essential is that some conducting medium, such as an iron rail, or a copper wire, shall form an unbroken connection between the motor apparatus and the central dynamo where the power is generated--the return circuit being made either by another wire or by the ordinary rails.

The central dynamo in question will be found, if we visit the power-house, to be a ponderous affair, suggestive to the untechnical mind of impenetrable mysteries. Yet in reality it is a device essentially the same in construction as the motor which drives the train. That is to say, its unit of construction consists of a wire-wound armature revolving on an axis and fitted between the poles of an electromagnet. Here, however, the sequence of phenomena is reversed, for the armature, instead of receiving a current of electricity, is made to revolve by a belt adjusted to its axis and driven by a steam engine. The wire coils of the armature thus made to revolve cut across the so-called lines of magnetic force which connect the two poles of the magnet, and in so doing generate a current of induced electricity, which flows away to reach in due course the third rail or the trolley-wire, and ultimately to propel the motor.

AN ELECTRIC TRAIN AND THE DYNAMO THAT PROPELS IT.

The lower figure gives an interior view of a power house of the Manhattan Elevated Railway Company. The upper figure shows one of the electric engines operating on the New York Central Lines just outside of New York. The power is conveyed to the engine by a third rail clearly shown in the picture.]

It is hardly necessary to state that in actual practice this generating dynamo is a complex structure. The armature is a complex series of coils of wire; the electromagnets surrounding the armature are several or many; and there is an elaborate system of so-called commutators through which the currents of electricity--which would otherwise oscillate as the revolving coil cuts the lines of magnetic force in opposite directions--are made to flow in one direction. But details aside, the foundation facts upon which everything depends are (1) that a coil of wire when forced to move so that it cuts across the lines of force in any magnetic field develops a so-called induced current of electricity; and (2) that such an induced current possesses power of magnetic attraction and repulsion. These facts were discovered more than sixty years ago, and carefully studied by Michael Faraday, Joseph Henry, and others. Faraday found that such an induced current could be produced not merely with the aid of an iron magnet, but even by causing a wire to cut the lines of force that everywhere connect the north and south poles of the earth,--the earth being indeed, as William Gilbert long ago demonstrated, veritably a gigantic magnet. Moreover, these relations are reciprocal; so that if a wire through which a current of electricity is passing is placed across a magnetic field, the wire is impelled to move in a plane at right angles to the direction of the lines of force. It is forcibly thrust aside. This side-thrust acting on coils of wire is what produces the revolution of the armature of the electric motor.

THE ORIGIN OF THE DYNAMO

The very first studies that had to do with the mutual relations of electricity and magnetism were made by Hans Christian Oersted, the Dane, as early as 1815. He discovered that a magnetic needle is influenced by the passage near it of a current of electricity, demonstrating, therefore, that the electric current in some way invades the medium surrounding any conductor along which it is passing. Oersted's experiments were repeated, and some new phenomena observed by the Frenchman André Marie Ampère and Dominique François Arago. Arago constructed an interesting device, in which a metal disk was made to revolve in the presence of a current of electricity; but neither he nor anyone else at the time was able to explain the phenomenon.

In 1824 an advance was made through the construction of the first electric magnet by Sturgeon. Hitherto it had not been known that a magnet could be made artificially, except by contact with a previously existing magnet. Sturgeon showed that any core of iron may be rendered magnetic if wound with a conducting wire, through which a current of electricity is passed. The experiments thus inaugurated were followed up in America by Joseph Henry of Albany who made enormous electromagnets, capable of sustaining great weights. One of his magnets, operated by a single cell, was able to lift six hundred and fifty pounds of metal.

It was this apparatus which was subsequently to make possible the utilization of electricity as a working force, but as yet no one suspected its possibilities in this direction.

It remained for Michael Faraday, in 1831, to make the final experiment which laid the secure foundation for the new science of electrodynamics. Faraday constructed a tiny apparatus, consisting of a magnet between the poles of which a metal disk was placed in such a way that it could revolve on an axis, the disk being connected with a wire conveying an electric current.

The details as to this most ingenious mechanism need not be given here. Suffice it that Faraday demonstrated the interrelations of magnetism and electricity and the possibility of causing a metal disk to revolve through this mutual interaction. In so doing he constructed the first dynamo-electric machine. In his hands it was a mere laboratory toy, but the principles involved were fully elaborated by the original experimenter, and stated in precise language which modern investigators have not been able to improve upon.

Several decades elapsed after Faraday's initial experiment before the phenomena of magneto-electricity were proved to have any considerable commercial significance. A vast amount of ingenuity was required to devise a mechanism which could advantageously utilize the principle in question for commercial purposes. Indeed the early experimenters did not at once get upon the right track, as their efforts were influenced disadvantageously by an attempt to follow the principle of the steam engine. Some interesting mechanisms were devised whereby the motion of an armature in being drawn toward an electromagnet could be translated into rotary motion through the use of crank-shafts and even of beams, precisely comparable to those employed in the steam engine. Such devices worked with a comparatively low degree of efficiency and were totally abandoned so soon as the idea of getting rotary motion directly from the magnet or armature was made feasible. The names of Saxton, Clarke, Woolrich, Wheatstone, and Werner Siemens are intimately connected with the early efforts at utilization of magneto-electric power. The shuttle-wound armature of Siemens, invented in 1854, marked an important progressive step.

PERFECTING THE DYNAMO

The first separately excited dynamos were constructed by Dr. Henry Wilde, F.R.S., between 1863 and 1865, and this invention paved the way for rapid progress. In 1866-7 Varley, Siemens, Wheatstone, and Ladd constructed machines with several iron electromagnets, self-excited, which were described as dynamo-electric machines, a term afterward contracted to dynamos. In 1867 Dr. Wilde improved the armature by introducing several coils arranged around a cylinder; the current from a few of the coils was rectified and used to excite the field magnet, while the main current as given off by the rest of the coils was taken off by ring-contacts, the machine being a self-exciting, alternating-current dynamo.

Dr. Wilde invented and patented (1863-5) the first separately excited dynamo, with which he demonstrated that the feeble current from a small magneto-electric machine would, by the expenditure of mechanical power, produce currents of great strength from a large dynamo.]

The Italian, Picnotti, in 1864 invented a ring armature which, although provided with teeth was wound with coils in such a way as to obtain a very uniform current; but the practical introduction of the continuous-current machines dates from 1870, when Gramme re-invented the ring and gave it the form which is still in vogue. Von Alteneck in 1873 converted the Siemens shuttle armature along the same lines and so introduced the drum arrangement which has since been very extensively adopted.

Thus through the efforts of a great number of workers the idea of utilizing electromagnetic energy for the purposes of the practical worker came to be a reality. Numberless machines have been made differing only as to details that need not detain us here. Everyone is familiar with sundry applications of the dynamo to the purposes of to-day's applied science. It must be understood, of course, that the amount of electricity generated in any dynamo is precisely measurable, and that by no possibility could the energy thus developed exceed the energy required to move the coils of wire. Were it otherwise the great law of the conservation of energy would be overthrown. In actual practice, of course, there is loss of energy in the transaction. The current of electricity that flows from the very best dynamo represents considerably less working power than is expended by the steam engine in forcibly revolving the armature. In the early days of experiments the loss was so great as to be commercially prohibitive. With the perfected modern dynamo the loss is not greater than fifteen per cent; but even this, it will be noted, makes electricity a relatively expensive power as compared with steam,--except, indeed, where some natural power, like the Falls of Niagara, can be utilized to drive the armature.

A MYSTERIOUS MECHANISM

The efficiency of the modern dynamo is due largely to the fact that when the poles of the magnet are made to face each other, the lines of magnetic force passing between these poles are concentrated into a narrow compass. With the ordinary bar magnet, as everyone is aware, these lines of force circle out in every direction from the poles in an almost infinite number of loops, all converging at the poles, and becoming relatively separated at the equator in a manner which may be graphically illustrated by the lines of longitude drawn on an ordinary globe.

It is obvious that with a magnet of such construction only a small proportion of the lines of magnetic force could be utilized in generating electricity. But, as already mentioned, when the magnet is so curved that its poles face each other, the lines of force, instead of widely diverging, pass from pole to pole almost in a direct stream. The strength of this magnetic stream may be increased almost indefinitely by winding the iron core of the magnet with the coil of wire through which the electric current is passed, thus constituting the electromagnet which has replaced the old permanent magnet in all modern commercial dynamos.

Fig. 1.--A small example of the original commercial form of the drum armature machine, patented in 1873 by Dr. Werner Siemens and F. Von Hefner Alteneck. The armature is a development of the Siemens shuttle form of 1856, and gives a nearly continuous current. Fig. 2.--An early experimental dynamo. Fig. 3.--Ferranti's original dynamo, patented in 1882-1883. The field magnets are stationary and consist of two sets of electro-magnets each with 16 projecting pull pieces, between which the armature revolves. Fig. 4.--The gigantic rotary converters of the Manhattan Elevated Railway.]

An electromagnet may be sufficiently powerful to lift tons of iron. The force it exerts, therefore, is very tangible in its results. Yet it seems mysterious, because so many substances are unaffected by it. You may place your head, for example, between the poles of the most powerful magnet without experiencing any sensation or being in any obvious way affected. You may wave your hand across the lines of force as freely as you may wave it anywhere else in space. Apparently nothing is there. But were you to attempt to pass a dumb-bell or a bar of iron across the same space, the unseen magnetic force would wrench it from your grasp with a power so irresistible as to be awe-inspiring.

Similarly, the armature, when its coils of wire are adjusted between the poles of the magnet, is held in a vise-like grip by the invisible but potent lines of magnetic force which tend to make it revolve. It requires a tremendous expenditure of energy--supplied by the steam-engine or by water power--to enable the coiled wires of the generating armature to stem the current of magnetic force, which is virtually what is done when the armature revolves in such a way as to produce electrical energy. Part of the mechanical energy thus expended is transformed into heat and dissipated into space; but the main portion is carried off, as we have seen, through the coiled wires of the armature in the form of what we term the current of electricity, to be re-transformed in due course into the mechanical energy that moves the car.

It appears, then, that the phenomena of the electric dynamo depend upon the curious relations that exist between magnetism and electricity. Granted the essential facts of magneto-electric induction, all the phenomena of the dynamo are explicable. But how explain these facts themselves? Why is an electric current generated in a coil of wire moving in a magnetic field? And why is a wire carrying a current of electricity, when placed across a magnetic field, impelled to move at right angles to the lines of magnetic force? No thoughtful person can consider the subject without asking these questions. But as yet no definitive answer is forthcoming. Some suggestive half-explanations, based on an assumed condition of torsion or strain in the ether, have been attempted, but they can hardly be called more than scientific guesses.

Meanwhile, it may be understood that the mutual relations of the magnetic and electrical forces just referred to are not at all dependent upon the manner in which the electric current is generated. The magneto-electric motor may be operated as well with a chemical battery as with such a mechanical generating dynamo as has just been described. The storage-batteries which have been employed in some street railways and those which propel the electric cabs about our city streets furnish cases in point. The only reason these are not more generally employed is that the storage battery has not yet been perfected so that it can produce a large supply of electricity in proportion to its weight, and produce it economically.

X

NIAGARA IN HARNESS

"Harnessing Niagara"--the phrase has been a commonplace for a generation; but until very recently indeed it was nothing more than a phrase. Almost since the time when the Falls were first viewed by a white man the idea of utilizing their powers has been dreamed of. But until our own day--until the last decade--science had not shown a way in which the great current could be economically shackled. A few puny mill-wheels have indeed revolved for thirty years or so, but these were of no greater significance than the thousands of others driven by mountain streams or by the currents of ordinary rivers. But about a decade ago the engineering skill of the world was placed in commission, and to-day Niagara is fairly in harness.

If you have ever seen Niagara--and who has not seen it?-you must have been struck with the metamorphosis that comes over the stream about half a mile above the falls. Above this point the river flows with a smooth sluggish current. Only fifteen feet have the waters sunk in their placid flowing since they left Lake Erie. But now in the course of half a mile they are pitched down more than two hundred feet. If you follow the stream toward this decline you shall see it undergo a marvelous change. Of a sudden the placid waters seem to feel the beckoning of a new impulse. Caught with the witchery of a new motion, they go swirling ahead with unwonted lilt and plunge, calling out with ribald voices that come to the ear in an inchoate chorus of strident, high-pitched murmurings. Each wavelet seems eager to hurry on to the full fruition of the cataract. It lashes with angry foam each chance obstruction, and gurgles its disapproval in ever-changing measures. Even to the most thoughtless observer the mighty current thus unchained attests the sublimity of almost irresistible power. Could a mighty mill-wheel be adjusted in that dizzy current, what labors might it not perform? Five million tons of water rush down this decline each hour, we are told; and the force that thus goes to waste is as if three million unbridled horses exhausted their strength in ceaseless plunging. This estimate may be only a guess, but it matters not whether it be high or low; all estimates are futile, all comparisons inadequate to convey even a vague conception of the majesty of power with which the mighty waters rush on to their final plunge into the abysm.

It is here, you might well suppose, where the appalling force of the current is made so tangible, that man would place the fetters of his harness, making the madcap current subject to his will. You will perhaps more than half expect to see gigantic mechanisms of man's construction built out over the rapids or across the face of the cataract--so much has been said of æstheticism versus commercialism in connection with the attempt to utilize Niagara's power. But whatever your fears in this regard, they will not be realized. Inspect the rapids and the falls as you may, you will see no evidence that man has tampered with their pristine freedom. Subtler means have been employed to tame the wild steed. The mad waves that go dashing down the rapids are as free and untrammeled to-day as they were when the wild Indian was the only witness of their tempestuous activity. Such portions of the current as reach the rapids have full license to pass on untrammeled, paying no toll to man. The water which is made to pay tribute is drawn from the stream up there above the rapids, where it lies placid and as yet unstirred by the beckoning incline. To see Niagara in harness, then, you must leave the cataract and the rapids and pass a full mile up the stream where the great river looks as calm as the Hudson or the Mississippi, and where, under ordinary conditions, not even the sound of the falls comes to your ear.

Prosaic enough it seems to observe here nothing more startling than a broad _cul de sac_ of stagnant water, like the beginning of a broad canal, extending in for a few hundred yards only from the main stream; its waters silent, currentless, seemingly impotent. This stagnant pool, then, not the whirling current below, is to furnish the water whose reserve force of energy of position is drawn upon to serve man's greedy purpose. Coming from the rapids and cataract to this stagnant canal, you seem to step from the realm of poetic beauty to the sordid realities of the work-a-day world. Of a truth it would seem that "harnessing Niagara" is but a far-fetched metaphor.

WITHIN THE POWER-HOUSE

And yet if you will turn aside from the canal and enter one of the long, low buildings that flank it on either side, you will soon be made to feel that the metaphor was amply justified. Little as there was exteriorly to suggest it, you are entering a fairyland of applied science, and within these plain walls you shall witness evidences of the ingenuity of man that should appeal scarcely less to your imagination than the sight of the cataract itself in all its sublimity of power.

For within these walls, by a miracle of modern science, the potential energy which resides in the water of the canal is transformed into an electrical current which is sent out over a network of wires to distant cities to perform a thousand necromantic tasks,--propelling a street car in one place, effecting chemical decompositions in another; turning the wheels of a factory here and lighting the streets of a city there; in short, subserving the practical needs of man in devious and wonderful ways.

Even as you gazed disdainfully at the stagnant canal, its waters, miraculously transformed, were propelling the trolley cars along the brink of the cliff over there on the Canadian shore, and at the same time were turning the wheels in many a factory in the distant city of Buffalo. After all, then, the quiet pool of water was not so prosaic as it seemed.

As you stand in the building where this wonderful transformation of power is effected, the noble simplicity of the vista heightens the mystery. The most significant thing that strikes the eye is a row of great mushroom-like affairs, for all the world like giant tops, that stand spinning--and spinning. These great tops are about a dozen feet in diameter. They are whirling, so we are told, at a rate of two hundred and fifty revolutions per minute. Hour after hour they spin on, never varying in speed, never faltering; day and night are alike to them, and one day is like another. They are as ceaselessly active, as unwearying as Niagara itself, whose power they symbolize; and, like the great Falls, they murmur exultingly as they work.

Each of the top-like dynamos generates 5000 horse-power.]

The giant tops which thus seem to bid defiance to the laws of motion are in reality electric dynamos, no different in principle from the electric generators with which some visit to a street-car power-house has doubtless made you familiar. The anomalous feature of these dynamos--in addition to their size--is found in the fact that they revolve on a vertical shaft which extends down into a hole in the earth for more than a hundred feet, and at the other end of which is adjusted a gigantic turbine water-wheel. Water from the canal is supplied this great turbine wheel through a steel tube or penstock, seven feet in diameter. As the turbine revolves under stress of this mighty column of water, the long shaft revolves with it, thus turning the electric generator at the other end of the shaft--the generator at which we are looking, and which we have likened to a giant top--without the interposition of any form of gearing whatever.

To gain a vivid mental picture of the apparatus, we must take an elevator and descend to the lower regions where the turbine wheel is in operation. As we pass down and down, our eyes all the time fixed on the vertical revolving shaft, which is visible through a network of bars and gratings, it becomes increasingly obvious that to speak of this shaft as standing in "a hole in the ground" is to do the situation very scant justice. A much truer picture will be conceived if we think of the entire power-house as a monster building, about two hundred feet high, all but the top story being underground. What corresponds to the ground floor of the ordinary building is located one hundred and fifty feet below the earth's surface; and it is the top story which we entered from the street level, thus precisely reversing the ordinary conditions.

PENSTOCKS AND TURBINES

As we descend now and reach at last the lowest floor of the building, we step out into a long narrow room, the main surface of which is taken up with a series of gigantic turnip-shaped mechanisms, each one having a revolving shaft at its axis; while from its side projects outward and then upward a seven-foot steel tube, for all the world like the funnel of a steamship. This seeming funnel--technically termed a penstock--is in reality the great tube through which the massive column of water finds access to the turbine wheel, which of course is incased within the turnip-shaped mechanism at its base.

As you stand there beside this great steel mechanism a sense of wonderment and of utter helplessness takes possession of you. As you glance down the hall at this series of great water conduits, and strain your eyes upward in the endeavor to follow the great funnel to its very end, an oppressive sense of the irresistible weight of the great column of water it supports comes to you, and you can scarcely avoid a feeling of apprehension. Suppose one of the great tubes were to burst?--we should all be drowned like rats in a hole. There is small danger, to be sure, of such a contingency; but it is well worth while to have stood thus away down here at the heart of the great power-house to have gained an awed sense of what man can accomplish toward rivaling the wonders of nature. To have stood an hour ago on the ice bridge at the foot of the most tremendous cataract in the world, where Nature exhausts her powers amidst the mad rush and roar of seething waters; and now to stand beneath this other column of water which effects a no less wonderful transformation of energy, serenely, silently,--is to have run such a gamut of emotions as few other hours in all your life can have in store for you.

A MIRACULOUS TRANSFORMATION OF ENERGY

There are eleven of these great turbine mechanisms, each with a supplying funnel of water and a revolving shaft extending upward to its companion dynamo, in the room in which we stand. Energy representing fifty-five thousand horse-power is incessantly transformed and made available for man's use in the subterranean building in which we stand. And there is not a pound of coal, not a lick of flame, not an atom of steam involved in the transformation. There are no dust-grimed laborers; there is no glare of furnace, no glow of heat, no stifling odor of burning fuel;--there is only the restful hum of the machinery that responds to the ceaseless flow of the silent and invisible waters. Day and night the mighty river here pulls away at its turbine harness; and man, having once adjusted that harness, may take his ease and enjoy the fruits of his ingenuity.

As we return now to the top of the building, we shall view the spinning dynamos with renewed interest, and a few facts regarding their output of energy may well claim our attention. In their principle of action, as we have seen, all dynamos are alike,--depending upon the mutual relations between the wire-wound armature and a magnetic field. In the present case the magnets are made to revolve and the armatures are stationary, but this is a mere detail. There is one feature of these dynamos, however, which is of greater importance,--the fact namely that they operate without commutators, and therefore produce alternating currents. This fact has an important bearing upon the distribution of the current. Each of the dynamos before us generates the equivalent of five thousand horse-power of energy. There are eleven such dynamos here before us; there are ten more in the power-house on the other side of the canal, giving a total of one hundred and five thousand horse-power for this single plant; and there are five such plants now in existence or in course of construction to utilize the waters of Niagara, three being on the Canadian shore. When in full operation the aggregate output of these plants will be six or seven hundred thousand horse-power.

SUBTERRANEAN TAIL-RACES

As we step from the door of the power-house and stand again beside the canal whose waters produce the wonderful effects we have witnessed in imagination, one question remains to be answered: What becomes of the water after it has passed through the turbine wheels down there in the depths? The answer is simple: All the water from the various turbines flows away into a great subterranean canal which passes down beneath the city of Niagara Falls, and discharges finally at the level of the rapids a few hundred yards below the Falls. The construction of this subterranean canal would in itself have been considered a great engineering feat a few decades ago; but of late years mountain tunnels, such subterranean railways as the London "tube system" and tunnels beneath rivers have robbed such structures of their mystery. It may be added that another such subterranean canal, to serve as a tail-race for one of the new Canadian plants, extends beneath the cataract itself, discharging not far from the centre of the Horseshoe Falls. Another of the power companies utilizes the water of the old surface canal which extends to the brink of the gorge some distance below the Falls. Yet another company on the Canadian side conveys water from far above the rapids in a gigantic closed tube to the brink of the gorge just below the Canadian Falls, above the point where their power-house is located.

But the principle involved is everywhere the same. The idea is merely to utilize the weight of falling water. The water of Niagara River is of course no different from any other body of water of equal size. It is merely that its unique position gives the engineer an easy opportunity to utilize the potential energy that resides in any body of water--or, for that matter, in any other physical substance--lying at a high level. In due course, doubtless, other bodies of water, such as mountain lakes and mountain streams will be similarly put into electrical harness. The electrical feature is of course the one that most appeals to the imagination. But it may be well to recall that the ultimate source of all the power in question is gravitation. People fond of philosophical gymnastics may reflect with interest that, according to the newest theory, gravitation itself is, in the last analysis, an electrical phenomenon--a reflection which, it will be noted, leads the mind through a very curious cycle.

THE EFFECT ON THE FALLS

Much solicitude has been expressed as to the possible effect, upon the Falls themselves, of this withdrawal of water. For the present, it is admitted, there is no visible effect; and to the casual observer it may seem that almost any quantity of water the power-houses are likely to need might be withdrawn without seriously marring the wonderful cataract. But the statistics supplied by the power companies, taken in connection with estimates as to the bulk of water that passes over the Falls, do not support this optimistic view. Taking what seems to be a reasonable estimate for a basis of computation it would appear that when the power-houses now rapidly approaching completion are in full operation, the total withdrawal of water from the stream will represent a very appreciable fraction of its entire bulk--one-twenty-fifth at the very least, perhaps as much as one-tenth. Such a diminution as this will by no means ruin the Falls, yet it would seem as if it must sensibly affect them, particularly at some places near Goat Island, where the water flows at present in a very shallow stream. Be that as it may, however, the power-houses are there, and it is probable that their number will be added to as years go on. Whether commercialism or æstheticism will win in the end, it remains for the legislators of the future to decide.

Meanwhile, it is gratifying to reflect that for the present the Falls retain their pristine beauty, even though part of the water that is their normal due is turned aside and made to do service for man in another way. There is only one reason why the Falls have escaped desecration so long as they have; that reason being the very practical one that until quite recently man has not known how to utilize their powers to advantage. The effort was indeed made, a full generation ago, through the construction of the canal leading from the upper river to the bluffs overlooking the gorge below the cataract. Here a few mill-wheels were set whirling, and a tiny fraction of the potential energy of the water was utilized. There was no mechanical difficulty involved in the utilization of this power. Mill-wheels are a familiar old-time device, and even the turbine wheel is modern only in a relative sense of the word. And it must be understood that the turbine water-wheel utilizes the greatest proportion of the power of falling water of any contrivance as yet known to mechanics. It was possible, then, to utilize the water of Niagara with full effectiveness fifty years ago, so far as the direct action of the water-wheel upon machinery near at hand was concerned. The sole difficulty lay in the fact that only a small amount of machinery can be placed in any one location. The real problem was not how to produce the power, but how to transmit it to a distance.

THE TRANSMISSION OF POWER

For fifty years mechanical engineers have looked enviously upon unshackled Niagara, and have striven to solve the problem of transmitting its power. It were easy enough to harness the great Fall, but futile to do so, so long as the power generated must be used in the immediate vicinity. So, many schemes for transmitting power were tried one after another, and as often laid aside. There was one objection to even the best of them--the cost. At one time it was thought that compressed air might solve the problem. But repeated experiments did not justify the hope. Then it was believed that the storage battery might be made available. The storage battery, it might be explained, does not really store electricity in the sense in which the Leyden jar, for example, stores it. Rather is it to be likened to an ordinary voltaic cell, the chemical ingredients of which have been rendered active by the passage of the electric current. The active ingredients of the storage battery are usually lead compounds, which through action of the electric currents have been decomposed and placed in a state of chemical instability. The dissociated molecule of the lead compound, when permitted to reunite with the atoms with which it was formerly associated, will give up electrical energy.

Such a storage battery might readily be charged with electricity generated at Niagara Falls. It might then be conveyed to any part of the world, and, its poles being connected, the charge of electricity would be made available. Such storage batteries are in common use in connection with electric automobiles, as we have seen. But the great difficulty is that they are enormously heavy in proportion to the amount of electricity that they can generate; therefore, their transportation is difficult and expensive. In practice it is cheaper to produce electricity through the operation of a steam engine in a distant city than to transmit the electricity with the aid of a storage battery from Niagara. So the storage battery served as little as compressed air to solve the engineer's problem.

When the electric dynamo became a commercial success for such purposes as the operation of trolley lines it seemed as if the Niagara problem was on the verge of solution. And so, in point of fact, it really was, though more time was required for it than at first seemed needed. The power generated by the dynamo could, indeed, be transmitted along a wire, but not without great loss. Sir William Siemens, in 1877, had pointed out in connection with this very subject of the wasted power of Niagara, that a thousand horse-power might be transmitted a distance of, say, thirty miles over a copper rod three inches in diameter. But a copper rod three inches in diameter is enormously expensive, and when Siemens further stated that sixty per cent of the power involved would be lost in transmission, it was obvious that the method was far too wasteful to be commercially practicable.

For a time the experimenters with the transmission of electricity along a wire were on the wrong track. They were experimenting with a continuous current which, as we have seen, is produced from an ordinary dynamo with the aid of a commutator. But hosts of experiments finally made it clear that this form of current, no matter how powerful it might be, is unable to traverse considerable distance without great loss, being frittered away in the form of heat.

But the very term "continuous current" implies the existence of a current that is not continuous. In point of fact, we have already seen that a dynamo, if not supplied with a commutator, will produce what is called an alternating current, and such a current has long been known to possess properties peculiar to itself. It is, in effect, an interrupted current, and it is sometimes spoken of as if it really consisted of an alternation of currents which move first in one direction and then in another. Such a conception is not really justifiable. The more plausible explanation is that the alternating current is one in which the electrons are not evenly distributed and move with irregular motion. Perhaps we may think of the individual electrons of such a current as oscillating in their flight, and, as it were, boring their way into the resisting medium. In any event, experience shows that such a current, under proper conditions, may be able to traverse a conducting wire for a long distance with relatively small loss.

It must be understood, however, that the mere fact that a current alternates is not in itself sufficient to make feasible its transmission to a remote distance. To meet all the requirements a current must be of very high voltage. This means, in so far as we can represent the conditions of one form of energy in the terms of another, that it shall be under high pressure. Fortunately a relatively simple apparatus enables the electrician to transform a current from low to high voltage without difficulty. And so at last the problem of transmitting power to a distance of many miles has been solved. Electrical currents representing thousands of horse-power are to-day transmitted from Niagara Falls to the city of Buffalo over ordinary wires, with a loss that is relatively insignificant. A plant is in process of construction that will similarly transmit the power to Toronto; and it is predicted that in the near future the powers of Niagara will be drawn upon by the factories of cities even as far distant as New York and Chicago. Practical difficulties still stand in the way of such very distant transmission, to be sure, but these are matters of detail, and are almost certain to be overcome in the near future.

All this being explained, it will be understood that the sole reason why the new power-houses at Niagara generate electricity is that electricity is the one readily transportable carrier of energy. We have already explained that there is loss of energy when the steam engine operates the dynamo. At Niagara, of course, no steam is involved; it is the energy of falling water that is transformed into the energy of the electrical current. Moreover, the revolving dynamo is attached to the same shaft with the turbine water-wheel, so that there is no loss through the interposition of gearing. Yet even so, the electric current that flows from the dynamo represents somewhat less of energy than the water current that flows into the turbine. This loss, however, is compensated a thousandfold by the fact that the energy of the electric current may now be distributed in obedience to man's will.

"STEP UP" AND "STEP DOWN" TRANSFORMERS

The dynamos in operation at Niagara do not differ in principle from those in the street-car power-house, except in the fact that they are not supplied with commutators. We have seen that these dynamos are of enormous size. Those already in operation generate five thousand horse-power; others in process of construction will develop ten thousand. The generator which produces this enormous current is about eleven feet in diameter, and it makes two hundred and fifty revolutions per minute. The armatures are so wound that the result is an alternating current of electricity of twenty-two hundred volts. This current represents, it has been said, raw material which is to be variously transformed as it is supplied to different uses. To factories near at hand, indeed, the current of twenty-two hundred volts is supplied unchanged; but for more distant consumption it is raised to ten thousand volts; and that portion which is sent away to the factories of Buffalo and other equally distant places is raised to twenty-two thousand volts.

The upper figure shows Ferranti's experimental transformer built in 1888. It has a closed iron circuit, built up of thin strips filling the interior of the coil and having their ends bent over and overlapping outside. The lower figure shows a simple transformer known as Sturgeon's induction coil. The middle figure gives a view of the series of converters in the power house of the Manhattan Elevated Railway.]

The transformation from a relatively low voltage to the high one is effected by means of what is called a step-up transformer. This is an apparatus which brings into play a principle of electric induction not very different from that which was responsible for the generation of the current of electricity in the dynamo. The principle is that evidenced in the familiar laboratory apparatus known as the Ruhmkorff coil. The transformer consists essentially of a primary coil of relatively large wire, surrounded by, but insulated from, a secondary coil of relatively fine wire. When the interrupted current is sent through the primary coil of such an apparatus, an induced counter-current is generated in the secondary coil. Of course there is no gain in the actual quantity of electricity, but the voltage of the current generated in the finer wire is greatly increased. For example, as we have seen, the current that came from the dynamo at twenty-two hundred volts is raised to ten thousand or twenty-two thousand volts. These proportions may be varied indefinitely by varying the relative sizes and lengths of the primary and secondary coils.

How shall we picture to ourselves the actual change in the current represented by this difference in voltage? We might prove, readily enough, that the difference is a real one, since a wire carrying a current of low voltage may be handled with impunity, while a similar wire carrying a current of high voltage may not safely be touched. But when we attempt to visualize the difference in the two currents we are all at sea. We may suppose, of course, that electrons spread out over a long stretch of the secondary coil must be more widely scattered. One can conceive that the electrons, thus relatively unimpeded, may acquire a momentum, and hence a penetrative power, which they retain after they are crowded together in a straight conductor. But this suggestion at best merely hazards a guess.