William Henry Preece

“ When we speak of electricity of a high potential, it has exactly the same meaning as high level of water, or of high temperature, and wherever two differences of potential are produced, separated by a conductor, electricity flows. Having said so much, perhaps too much, I want to speak to you about the production of electricity. Having shown you the various forms of energy, how it is transferred, and why it is transferred, I want now to say something of the production of electricity. ”

“ We sometimes hear electricity spoken of as a mysterious agency, and sometimes as a wild, untamed beast. It is only mysterious to the ignorant, and it is only untamed to the unskilled. I hope that the promise I made to you at first starting, that you would leave this room with a fair knowledge of how the electric light is produced, has been fulfilled, and I can only add that electricity will always prove an obedient slave to those who take the trouble to understand it ”

“ Our tides abstract energy from the earth, which is gradually robbing the earth of its motion, and the result is that our day is getting longer and longer. If any of you live a million years, you will probably find that the day will be a minute longer than it is now! ”

“ A moving cricket-ball is a good example of kinetic energy. In its passage through the air it possesses kinetic energy, and should the ball catch your head you know pretty well what is the effect. A steamship moving and a running railway-train are kept in motion by the energy imparted to them from coal, and we know what tremendous energy a steamship or a railway-train has, as when a collision occurs there is a terrific smash-up. Our earth is another magnificent store of energy in its rotation every twenty-four hours ”

“ Lecturing, for instance, is a considerable exercise of energy. A man can lecture pretty well for an hour; he can lecture not quite so well for two hours, but the best lecturer in the world can scarcely keep at it for three hours without losing all his energy, and, like the crew in the boat, being thoroughly pumped out. This energy—or work done, as I have said—is measurable. The gardener who moves his ton of gravel three feet high has done an amount of work that any boy can calculate who will reduce one ton to pounds, and multiply that sum by three. ”

“ The electric light is coincident with electric heat; the art of producing a brilliant light is the art of producing a high temperature. No greater illusion is extant than the idea that the electric light is a cold light, for the electric arc is the greatest source of heat known. This heat can be produced either by causing the electricity to fly across an air-space, in which case we have light by the arc, or an arc light, or by causing it to flow through a small wire or a carbon filament, which offers obstruction to the flow and produces light by incandescence, or the incandescent light. ”

“ Some of it must always be wasted, and the true economist will try and waste the least possible quantity. If I place a piece of platinum wire between the two wires connected with the hand dynamo-machine, you see that the muscular energy of my assistant, by turning the handle, generates currents of electricity, which give a red heat to the platinum wire. The energy of the body is thrown into the machine, the machine converts it into electricity, the electricity passes through the wire, which, by having work done upon it, is rendered incandescent, and, in consequence, becomes luminous. ”

“ I have shown you that energy is a form of motion; that it is so found in sound, heat, and light; but we also have energy as magnetism. There is a little toy-duck floating on the basin of water before me, and I merely hold in front of it a magnet, when you will see that a sort of affection is set up between the duck and the magnet, by the duck following the motion of the magnet round the basin. That is another form of energy. The last form of energy that I wish to draw your special attention to is that due to electricity. ”

“ The energy gained or lost is the quantity of work done on a body, or done by that body; so I want you to grasp, if you possibly can, the fact that every case of motion on this earth—even the sound of my voice, as I now speak to you—is due to the exercise of this particular energy. ”

“ Here is the dome of a bell, which I strike with a mallet or hammer, and thereby impart energy to it, and it sets the whole air of this room in motion, and every tympanum of every ear present is struck by the little bullets of air that are thrown into vibration, and the result is the effect called sound. ”

“ The tendency is to produce a common level, and the passage of water from the higher to the lower level produces motion and energy. Tides are simply the result of the effort to produce equilibrium in the sea after it has been attracted in different directions by the force of the sun or the moon. Rivers flow because the water high up in the mountains is at a higher level than the ocean, and the purpose of their flowing is to produce equilibrium, or an equality of level. Heat circulates in our rooms because a higher temperature exists in the fire than in the walls. ”

“ Machines, working with high velocity, great steadiness, and uniform pressure, have solved the problem of cheap electricity. The amount of coal required to produce one horse-power has been reduced from seven and eight pounds to three and even two pounds. The gas-engine—a very economical source of energy—has been successfully applied to electric lighting in many places. Such an engine has been used at the docks in Newport, South Wales, to produce a light of eleven times the power that the same gas would give if used directly. Here is a sphere in which gas companies may maintain their dividends. ”

“ The brilliancy of a well-lighted room is simply enchanting. The purity of the light for the transaction of business, the selection of colors, and the ordinary daily avocations of life, is simply superb. Its cleanliness is one of its great merits. It emits no smoke. Probably its greatest advantage is to be found in the influence it exerts on health. At Glasgow, where the light has been applied, all causes of trouble arising from the vitiation which was occasioned by other lights have ceased. Health has been engendered, and more work has been got out of the men ”

“ It remains quiescent until heat is applied, when its potential form of energy is at once transformed into its active or kinetic form, impelling a cannon-ball or bullet with tremendous force. Coal, again, is a grand store of energy. All our steam-engines employed in manufactures are set going by the energy that is stored up in coal. This energy has remained stored up in coal for millions of years in the bowels of the earth, it is brought to the surface, and is there used to produce power in the innumerable ways with which you are acquainted. ”

“ That which has gone out of the crew, and out of the boy who threw the cricket-balls, is what we call energy, and what they have done is to do work upon the boat. Another example is in the case of foot-ball. A boy kicks a foot-ball and makes a splendid goal. To do that he has sent something out of his body into the ball which hurtles through the air past the goal, and the game is won. In all these illustrations something is done which results in fatigue, work is performed and energy is lost; in fact, work done means energy applied, and energy applied means work done. ”

“ As mental energy is our capacity for learning lessons, for going through examinations, and that kind of thing, so the energy of the kind I speak of is the capacity for doing absolute physical work. The generality of this energy is immense. It is a difficult thing to grasp the fact that there is something in existence that we can not feel, that we can not touch, and that we can not see, but which gives us all the force and all the power we possess. The earth as it moves around the sun and the earth as it daily rotates upon its own axis are instances of the existence of this energy ”

“ Instead of having only one rod, or one wire, we have in this hand-machine an arrangement of a thousand turns of wire; instead of having the weak magnetism of the earth, we have the powerful field of permanent magnet; and, instead of causing it to move through the air by the velocity of my arm, we apply multiplying gear, which, as you see, imparts velocity to it of great rapidity. Thus motion, through a magnetic field, produces an electro-motive force. There never can be a continuous electro-motive force without some source of energy. ”

“ Many have tried the light and abandoned it. In some cases its economy is unquestionable, but there are places where careful persons have shown that gas, as regards economy, surpasses it. It is questionable whether, in some cases, the electric light does not affect the eye. The arc-light produces, also, nitrous acid and other deleterious gases, but the incandescent lamp is free from this trouble. The powerful currents that it requires can not be carried over buildings and rooms without incurring danger from fire and to life. Nevertheless, the light has great and manifold advantages. ”

“ Why are meteorologists able to tell us that there is a gale coming? Because they know that there is a higher pressure at one spot than there is on another; and where there is a difference of pressure there must be motion of air. ”

“ Again, we have energy transferred from the sun to the earth by that thin, almost immaterial, subtile medium called the ether, by means of which we have motion transferred from the sun to the earth, which gives us at one moment light, at another moment heat, and at a third moment those effects that result in photographs. Energy is also transferred through matter in the shape of heat. ”

“ The carbon is extremely thin as thin as a human hair but, in spite of its extreme tenuity, you see [knocking a lamp on the table] that concussion or shaking does not cause it to break, but it possesses great resilience, and vibrates like a steel spring; and it is so refractory that it will stand electric currents of enormous strength. As I have said, the lamps before you are worked by electric currents generated by an Edison dynamo-machine on the Thames embankment, but each lamp is self-regulating and can be turned on and off by turning a tap very like those used on gas-brackets. ”

“ The advocates of subdivision assume an inexhaustible source of electricity. Their opponents reply that there is but a very limited source of energy in every dynamo-electric machine. It may be that more powerful machines and lamps of lower resistance may enable us to light up a greater number on one circuit, but this is not subdivision, it is multiplication. ”

“ We have heard of the danger from fire through its use in theatres and houses, but I want to show you that, when I place a cambric pocket handkerchief round a lamp, which I then break while electricity is going through it, no spark or fire of any kind occurs, but the lamp instantly goes out. There is also danger from wires coming in contact with each other, and in that case they short circuit the machine; they cause an increased strength of current to flow, producing heat, and in that manner setting fire to houses. ”

“ The difference in the value of the several excellent machines employed for generating the current is not great. Each is especially adapted for its own particular work, either by a variation in velocity or by a variation in the manner in which the wire is wound, so as to produce a variation in the current produced to suit the particular light required. In both the Siemens and the Gramme machines ninety per cent, of the power is converted into useful current. It is easily demonstrable that there is economy in the use of small machines. ”

“ The earth is an enormous magnet—a fact which we know, because our compasses guide the mariners across the deep. The air in this room is under the influence of the earth's magnetism; and if I move a wire or rod within that influence, at right angles to the lines of magnetic force, I cause it to be electrified, but only to an excessively small extent. The strength of the current produced depends upon the strength of the magnetic field, and upon the velocity with which the conductor moves across the field. ”

“ Energy expended in one part of a circuit must be given out at another. If zinc is consumed in a battery, it generates a certain amount of energy; that energy must be evident in some other part of the circuit, and the heat you saw in the platinum was really the heat that would have appeared in the battery itself if we had not caused the current to flow through a solid conductor which offered a considerable amount of resistance to its progress, as compared with the resistance in the battery itself. ”

“ One steam-engine is known from another by its being able to exercise ten, twenty, or fifty horse-power; and so, whether it is merely the lifting of gravel—or a small tube, such as I have here—throwing a cricket-ball, moving a boat, or working a steam-engine, it can all be measured by this simple unit of foot-pounds. Two other terms are necessary in order to make you comprehend what energy is. Energy is found in two conditions—called "potential" from its position, and "kinetic" from its motion. ”

“ The exhibition will be well worth a visit; in fact, all exhibitions are worth visiting, for they excite interest, they induce every one, more or less, by generating curiosity, to add to his knowledge, they honestly stimulate national as well as individual competition, and they always result in the enlargement of the useful application of a power like that of electricity, because a man of one trade who sees electricity used in another trade can not resist thinking out whether it can not also be usefully applied to his own purposes. ”

“ I touch the lamps before me and feel them warm because the heat of the incandescent material which they contain has thrown the molecules of the covering glass into vibration, and that vibration imparts a vibration to my hand that gives the sensation of heat; and if I were to put a poker in the fire—which, no doubt, all of you have done—it would be found in a very short time that the heat of the fire had been transferred through the poker to your hand. Electric currents are a form of energy which is driven through matter. Electricity is transferred, principally, through metals ”