MILITARY PORTABLE ELECTRIC LIGHT AT THE PARIS EXHIBITION.MILITARY PORTABLE ELECTRIC LIGHT AT THE PARIS EXHIBITION.
MILITARY PORTABLE ELECTRIC LIGHT AT THE PARIS EXHIBITION.
It consists of a tubular boiler (Dion, Bouton & Trepardoux system). This generator is easily taken to pieces, cleaned, and repaired, and steam can be raised to working pressure in 20 minutes. The mechanical and electrical part of the apparatus consists of a Parsons turbo-motor, of which MM. Sautter, Lemonnier & Co. possess the license in France for application to military and naval purposes. The speed of the motor is 9,000 revolutions per minute, and the dynamo is driven direct from it; at this speed it gives a current of 100 amperes with and from 55 to 70 volts; the intensity of the light is from 5,500 to 6,000 carcels. The carriage upon which the whole of this apparatus is mounted is carried on four wheels, made of wood with gun metal mountings. These are more easy to repair when in service than if they were wholly of iron. The weight of the carriage is three tons.—Engineering.
Prof. Galileo Ferraris, of Turin, who has carefully studied alternating currents and secondary transformers, has constructed a little motor based upon an entirely new principle, which is as follows: If we take two inductive fields developed by two bobbins, the axes of which cut each other at right angles, and a pole placed at the vertex of the angle, this pole will be subjected to the simultaneous action of the two bobbins, and the resultant of the magnetic actions will be represented in magnitude and direction by the diagonal of the parallelogram, two consecutive sides of which have for their length the intensity of the two fields, and for their direction the axes of the two bobbins.
If into each of these bobbins we send alternating currents having between one bobbin and the other a difference of phase of 90°, the extremity of the resultant will describe a circle having for its center the vertex of the right angle.
If, instead of a fixed pole, we use a metal cylinder movable on its axis, we shall obtain a continuous rotatory motion of this part, and the direction of the movement will change when we interchange the difference of phase in the exciting currents. This rotatory movement is not due to the Foucault currents, for the metal cylinder may consist of plates of iron insulated from each other.
In order to realize the production of these fields, several means can be employed: The current is sent from an alternating current machine into the primary circuit of a transformer and thence into one of the bobbins, the other being supplied by means of the secondary current of the transformer. A resistance introduced into the circuit will produce the required difference of phase, and the equality of the intensities of the fields will be obtained by multiplying the number of turns of the secondary wire on the bobbin. Moreover, the two bobbins may be supplied by the secondary current of a transformer by producing the difference of phase, as in the first case.
In the motor constructed by Prof. Ferraris the armature consisted of a copper cylinder measuring 7 centimeters in diameter and 15 centimeters in length, movable on its axis. The inductors were formed of two groups of two bobbins. The bobbins which branched off from the primary circuit of a Gaulard transformer, and were connected in series, comprised 196 spirals with a resistance of 13 ohms; the bobbins comprising the secondary circuit were coupled in parallel, and had 504 spirals with 3.43 ohms resistance. In order to produce the difference of phase, a resistance of 17 ohms was introduced into the second circuit, when the dynamo produced a current of 9 amperes with 80 inversions per second. Under these conditions the available work measured on the axis of the motor was found for different speeds: Revolutions per minute: 262—400—546—650—722—770. Watts measured at the brake: 1.32—2.12—2.55—2.77—2.55—2.40. The maximum rendering corresponds to a speed of rotation of 650 revolutions, and Prof. Ferraris attributes the loss of work for higher speeds to the vibrations to which the machine is exposed. At present the apparatus is but a laboratory one.—Bulletin International de l'Electricite.
The application of electricity for our convenience and comfort is one of the marvels of the age. Never in the history of the world has there been so rapid a development of an occult science. Prior to 1819 very little was known in regard to magnetism and electricity. During that year Oersted discovered that an electric current would deflect a magnetic needle, thus showing that there was some relationship between electric and magnetic force. A few months later, Arago and Sir Humphry Davy, independently of each other, discovered that by coiling a wire around a piece of iron, and passing an electric current through it, the iron would possess for the time being all the properties of a magnet. In 1825 William Sturgeon, of London, bent a piece of wire in the form of the letter U, wound a second wire around it, and, upon connecting it with a galvanic battery, discovered that the first wire became magnetic, but lost its magnetic property the moment the battery was disconnected. The idea of a telegraphic signal came to him, but the electric impulse, through his rude apparatus, faded out at a distance of fifty feet. In 1830 Prof. Joseph Henry, of this country, constructed a line of wire, one and a half miles in length, and sent a current of electricity through it, ringing a bell at the farther end. The following year Professor Faraday discovered magnetic induction. This, in brief, is the genesis of magnetic electricity, which is the basis of all that has been accomplished in electrical science.
The first advance after these discoveries was in the development of the electric telegraph—the discovery in 1837, by the philosopher Steinhill, that the earth could serve as a conductor, thus requiring but one wire in the employment of an electric current. Simultaneously came Morse's invention of the mechanism for the telegraph in 1844, foreshadowed by Henry in the ringing of bells, thus transmitting intelligence by sound. Four years later, in 1848, Prof. M. G. Farmer, still living in Eliot, Me., attached an electro-magnet to clockwork for the striking of bells to give an alarm of fire. The same idea came to William F. Channing. The mechanism, constructed simply to illustrate the idea by Professor Farmer, was placed upon the roof of the Court House in Boston, and connected with the telegraph wire leading to New York, and an alarm rung by the operator in that city. The application of electricity for giving definite information to firemen was first made in Boston, and it was my privilege to give the first alarm on the afternoon of April 12, 1852.
At the close of the last century, Benjamin Thompson, born in Woburn, Mass., known to the world as Count Rumford, was in the workshop of the military arsenal of the King of Bavaria in Munich, superintending the boring of a cannon. The machinery was worked by two horses. He was surprised at the amount of heat which was generated, for when he threw the borings into a tumbler filled with cold water, it was set to boiling, greatly to the astonishment of the workmen. Whence came the heat? What was heat? The old philosopher said that it was an element. By experiment he discovered that a horse working two hours and twenty minutes with the boring machinery would heat nineteen pounds of water to the boiling point. He traced the heat to the horse, but with all his acumen he did not go on with the induction to the hay and oats, to the earth, the sunshine and rain, and so get back to the sun. One hundred years ago there was no chemical science worthy of the name, no knowledge of the constitution of plants or the properties of light and heat. The old philosophers considered light and heat to be fluids, which passed out of substances when they were too full. Count Rumford showed that motion was convertible into heat, but did not trace the motion to its source, so far as we know, in the sun.
It is only forty-six years since Professor Joule first demonstrated the mutual relations of all the manifestations of nature's energy. Thirty-nine years only have passed since he announced the great law of the convertibility of force. He constructed a miniature churn which held one pound of water, and connected the revolving paddle of the churn with a wheel moved by a pound weight, wound up the weight, and set the paddle in motion. A thermometer detected the change of temperature and a graduated scale marked the distance traversed by the descending weight. Repeated experiments showed that a pound weight falling 772 feet would raise the temperature of water one degree, and that this was an unvarying law. This was transferring gravitation to heat, and the law held good when applied to electricity, magnetism, and chemical affinity, leading to the conclusion that they were severally manifestations of one universal power.—Congregationalist.
The opening of the new station of the Electric Lighting Co., of Salem, Mass., was recently celebrated with appropriate festivities.
Among the letters of regret from those unable to attend the opening was the following from Prof. Moses G. Farmer:
"Eliot, Me., Aug. 5, 1889.
"To the Salem Electric Lighting Company, Charles H. Price, President:
"Gentlemen: It would give me great pleasure to accept your kind invitation to be present at the opening of your new station in Salem on the 8th of this present August.
"It is now thirty years since the first dwelling house in Salem was lighted by electricity. That little obscure dwelling, 11 Pearl Street, formerly owned by 'Pa' Webb, had the honor to be illuminated by the effulgent electric beam during every evening of July, 1859, as some of your honored residents, perhaps, well remember. Mr. George D. Phippen can doubtless testify to one or more evenings; Mr. Wm. H. Mendell, of Boston, can also add his testimony; dozens of others could also do the same, had not some of them already passed to the 'great beyond,' among whom I well recollect the interest taken by the late and honored Henry L. Williams, Mr. J. G. Felt, and I do not know how many others. I well remember reading some of the very finest print standing with my back to the front wall and reading by the light of a 32 candle power lamp on the northernmost end of the mantel piece in the parlor; very possibly the hole in which the lamp was fastened remains to this day. In a little closet in the rear sleeping room was a switch which could be turned in one direction and give a beautiful glow light, while if turned in the other direction, it instantly gave as beautiful a dark. My then 12 year old daughter used to surprise and please her visitors by suddenly turning on and off the 'glim.' It is not well to despise the day of small things, for although the dynamo had not at that date put in an appearance, and though I used thirty-six Smee cells of six gallons capacity each, yet I demonstrated then and there that the incandescent electric light was a possibility, and although I innocently remarked to the late Samuel W. Bates, of Boston, who with his partner, Mr. Chauncey Smith, furnished so generously in the interest of science, not wholly without hope of return, the funds for the experiment, that it 'did not take much zinc,' and though Mr. Bates as naively replied, 'I notice that it takes some silver, though,' stillit was then and there heralded as the coming grand illuminant for the dwelling. I am thankful to have lived to see my predictions partly fulfilled.
"During the early fifties I published a statement something like this: 'One pound of coal will furnish gas enough to maintain a candle light for fifteen hours. One pound of gas (the product of five pounds of coal) will, in a good fishtail gas burner, furnish one candle light for seventy-five hours. One pound of coal burned in a good furnace, under a good boiler, driving a good steam engine, turning a good magneto-electric machine, will give a candle light for one thousand hours. But if all the energy locked up in one pound of pure carbon could be wholly converted into light, it would maintain one candle light for more than one and a half years.'
"So, gentlemen,nil desperandum; there is still room for improvement. Let your motto be 'Excelsior.' Possibly you may have already extracted from one-fifteenth to one-twelfth of the energy stored in the pound of carbon, but hardly more. Go on, go on, and bring it so cheap as to reach the humblest dwelling when you shall celebrate the centennial of the opening of your new station.
"I do most sincerely regret that I cannot be with you in the flesh. I am, like Ixion of old, confined to a wheel (chair in my case), cannot walk, cannot even stand; hence, owing to the impairment of my understanding (???), I must wish you all the enjoyments of the evening, and gladly content myself that you have made so much possible.
"Very truly yours,Moses G. Farmer."
To persons occupied in other branches of learning, and not directly engaged in the study of physical science, some rumor must probably have traveled of the stir and activity manifest at the present time among the votaries of that department of knowledge.
It may serve a useful purpose if I try and explain to outsiders what this stir is mainly about, and why it exists. There is a proximate and there is an ultimate cause. The proximate cause is certain experiments exhibiting in a marked and easily recognizable way the already theoretically predicted connection between electricity and light. The ultimate cause is that we begin to feel inklings and foretastes of theories, wider than that of gravitation, more fundamental than any theories which have yet been advanced; theories which if successfully worked out will carry the banner of physical science far into the dark continent of metaphysics, and will illuminate with a clear philosophy much that is at present only dimly guessed. More explicitly, we begin to perceive chinks of insight into the natures of electricity, of ether, of elasticity, and even of matter itself. We begin to have a kinetic theory of the physical universe.
We are living, not in a Newtonian, but at the beginning of a perhaps still greater Thomsonian era. Greater, not because any one man is probably greater than Newton,2but because of the stupendousness of the problems now waiting to be solved. There are a dozen men of great magnitude, either now living or but recently deceased, to whom what we now know toward these generalizations is in some measure due, and the epoch of complete development may hardly be seen by those now alive. It is proverbially rash to attempt prediction, but it seems to me that it may well take a period of fifty years for these great strides to be fully accomplished. If it does, and if progress goes on at anything like its present rate, the aspect of physical science bequeathed to the latter half of the twentieth century will indeed excite admiration, and when the populace are sufficiently educated to appreciate it, will form a worthy theme for poetry, for oratorios, and for great works of art.
To attempt to give any idea of the drift of progress in all the directions which I have hastily mentioned, to attempt to explain the beginnings of the theories of elasticity and of matter, would take too long, and might only result in confusion. I will limit myself chiefly to giving some notion of what we have gained in knowledge concerning electricity, ether, and light. Even that is far too much. I find I must confine myself principally to light, and only treat of the others as incidental to that.
For now well nigh a century we have had a wave theory of light; and a wave theory of light is quite certainly true. It is directly demonstrable that light consists of waves of some kind or other, and that these waves travel at a certain well-known velocity, seven times the circumference of the earth per second, taking eight minutes on the journey from the sun to the earth. This propagation in time of an undulatory disturbance necessarily involves a medium. If waves setting out from the sun exist in space eight minutes before striking our eyes, there must necessarily be in space some medium in which they exist and which conveys them. Waves we cannot have unless they be waves in something.
No ordinary medium is competent to transmit waves at anything like the speed of light; hence the luminiferous medium must be a special kind of substance, and it is called the ether. Theluminiferousether it used to be called, because the conveyance of light was all it was then known to be capable of; but now that it is known to do a variety of other things also, the qualifying adjective may be dropped.
Wave motion in ether, light certainly is; but what does one mean by the term wave? The popular notion is, I suppose, of something heaving up and down, or, perhaps, of something breaking on the shore in which it is possible to bathe. But if you ask a mathematician what he means by a wave, he will probably reply that the simplest wave is
y=asin (pt-nx),
and he might possibly refuse to give any other answer.
And in refusing to give any other answer than this, or its equivalent in ordinary words, he is entirely justified; that is what is meant by the term wave, and nothing less general would be all-inclusive.
Translated into ordinary English the phrase signifies "a disturbance periodic both in space and time." Anything thus doubly periodic is a wave; and all waves, whether in air as sound waves, or in ether as light waves, or on the surface of water as ocean waves, are comprehended in the definition.
What properties are essential to a medium capable of transmitting wave motion? Roughly we may say two—elasticityandinertia. Elasticity in some form, or some equivalent of it, in order to be able to store up energy and effect recoil; inertia, in order to enable the disturbed substance to overshoot the mark and oscillate beyond its place of equilibrium to and fro. Any medium possessing these two properties can transmit waves, and unless a medium possesses these properties in some form or other, or some equivalent for them, it may be said with moderate security to be incompetent to transmit waves. But if we make this latter statement, one must be prepared to extend to the terms elasticity and inertia their very largest and broadest signification, so as to include any possible kind of restoring force and any possible kind of persistence of motion respectively.
These matters may be illustrated in many ways, but perhaps a simple loaded lath or spring in a vise will serve well enough. Pull aside one end, and its elasticity tends to make it recoil; let it go, and its inertia causes it to overshoot its normal position; both causes together cause it to swing to and fro till its energy is exhausted. A regular series of such springs at equal intervals in space, set going at regular intervals of time one after the other, gives you at once a wave motion and appearance which the most casual observer must recognize as such. A series of pendulums will do just as well. Any wave-transmitting medium must similarly possess some form of elasticity and of inertia.
But now proceed to ask what is this ether which in the case of light is thus vibrating? What corresponds to the elastic displacement and recoil of the spring or pendulum? What corresponds to the inertia whereby it overshoots its mark? Do we know these properties in the ether in any other way?
The answer, given first by Clerk Maxwell, and now reiterated and insisted on by experiments performed in every important laboratory in the world, is:
The elastic displacement corresponds to electrostatic charge (roughly speaking, to electricity).
The inertia corresponds to magnetism.
This is the basis of the modern electro-magnetic theory of light. Now let me illustrate electrically how this can be.
The old and familiar operation of charging a Leyden jar—the storing up of energy in a strained dielectric, any electrostatic charging whatever—is quite analogous to the drawing aside of our flexible spring. It is making use of the elasticity of the ether to produce a tendency to recoil. Letting go the spring is analogous to permitting a discharge of the jar—permitting the strained dielectric to recover itself, the electrostatic disturbance to subside.
In nearly all the experiments of electrostatics, ethereal elasticity is manifest.
Next consider inertia. How would one illustrate the fact that water, for instance, possesses inertia—the power of persisting in motion against obstacles—the power of possessing kinetic energy? The most direct way would be to take a stream of water and try suddenly to stop it. Open a water tap freely and then suddenly shut it. The impetus or momentum of the stopped water makes itself manifest by a violent shock to the pipe, with which everybody must be familiar. The momentum of water is utilized by engineers in the "water ram."
A precisely analogous experiment in electricity is what Faraday called "the extra current." Send a current through a coil of wire round a piece of iron, or take any other arrangement for developing powerful magnetism, and then suddenly stop the current by breaking the circuit. A violent flash occurs if the stoppage is sudden enough, a flash which means the bursting of the insulating air partition by the accumulated electro-magnetic momentum.
Briefly, we may say that nearly all electro-magnetic experiments illustrate the fact of ethereal inertia.
Now return to consider what happens when a charged conductor (say a Leyden jar) is discharged. The recoil of the strained dielectric causes a current, the inertia of this current causes it to overshoot the mark, and for an instant the charge of the jar is reversed; the current now flows backward and charges the jar up as at first; back again flows the current, and so on, charging and reversing the charge with rapid oscillations until the energy is all dissipated into heat. The operation is precisely analogous to the release of a strained spring or to the plucking of a stretched string.
But the discharging body thus thrown into strong electrical vibration is embedded in the all-pervading ether, and we have just seen that the ether possesses the two properties requisite for the generation and transmission of waves—viz., elasticity and inertia or density; hence, just as a tuning fork vibrating in air excites aerial waves or sound, so a discharging Leyden jar in ether excites ethereal waves or light.
Ethereal waves can therefore be actually produced by direct electrical means. I discharge here a jar, and the room is for an instant filled with light. With light, I say, though you can see nothing. You can see and hear the spark indeed—but that is a mere secondary disturbance we can for the present ignore—I do not mean any secondary disturbance. I mean the true ethereal waves emitted by the electric oscillation going on in the neighborhood of this recoiling dielectric. You pull aside the prong of a tuning fork and let it go; vibration follows and sound is produced. You charge a Leyden jar and let it discharge; vibration follows and light is excited.
It is light just as good as any other light. It travels at the same pace, it is reflected and refracted according to the same laws; every experiment known to optics can be performed with this ethereal radiation electrically produced, and yet you cannot see it. Why not? For no fault of the light; the fault (if there be a fault) is in the eye. The retina is incompetent to respond to these vibrations—they are too slow. The vibrations set up when this large jar is discharged are from a hundred thousand to a million per second, but that is too slow for the retina. It responds only to vibrations between 4,000 billions and 7,000 billions per second. The vibrations are too quick for the ear, which responds only to vibrations between 40 and 40,000 per second. Between the highest audible and the lowest visible vibrations there has been hitherto a great gap, which these electric oscillations go far to fill up. There has been a great gap simply because we have no intermediate sense organ to detect rates of vibration between 40,000 and 4,000,000,000,000,000 per second. It was, therefore, an unexplored territory. Waves have been there all the time in any quantity, but we have not thought about them nor attended to them.
It happens that I have myself succeeded in getting electric oscillations so slow as to be audible. The lowest I have got at present are 125 per second, and for some way above this the sparks emit a musical note; but no one has yet succeeded in directly making electric oscillations which are visible, though indirectly every one does it when they light a candle.
Here, however, is an electric oscillator, which vibrates 300 million times a second, and emits ethereal waves a yard long. The whole range of vibrations between musical tones and some thousand million per second is now filled up.
These electro-magnetic waves have long been known on the side of theory, but interest in them has been immensely quickened by the discovery of a receiver or detector for them. The great though simple discovery by Hertz of an "electric eye," as Sir W. Thomson calls it, makes experiments on these waves for the first time easy or even possible. We have now a sort of artificial sense organ for their appreciation—an electric arrangement which can virtually "see" these intermediate rates of vibration.
The Hertz receiver is the simplest thing in the world—nothing but a bit of wire or a pair of bits of wire adjusted so that when immersed in strong electric radiation they give minute sparks across a microscopic air gap.
The receiver I have here is adapted for the yard-long waves emitted from this small oscillator; but for the far longer waves emitted by a discharging Leyden jar an excellent receiver is a gilt wall paper or other interrupted metallic surface. The waves falling upon the metallic surface are reflected, and in the act of reflection excite electric currents, which cause sparks. Similarly, gigantic solar waves may produce auroræ; and minute waves from a candle do electrically disturb the retina.
The smaller waves are, however, far the most interesting and the most tractable to ordinary optical experiments. From a small oscillator, which may be a couple of small cylinders kept sparking into each other end to end by an induction coil, waves are emitted on which all manner of optical experiments can be performed.
They can be reflected by plain sheets of metal, concentrated by parabolic reflectors, refracted by prisms, concentrated by lenses. I have at the college a large lens of pitch, weighing over three hundredweight, for concentrating them to a focus. They can be made to show the phenomenon of interference, and thus have their wave length accurately measured. They are stopped by all conductors and transmitted by all insulators. Metals are opaque, but even imperfect insulators such as wood or stone are strikingly transparent, and waves may be received in one room from a source in another, the door between the two being shut.
The real nature of metallic opacity and of transparency has long been clear in Maxwell's theory of light, and these electrically produced waves only illustrate and bring home the well known facts. The experiments of Hertz are in fact the apotheosis of that theory.
Thus, then, in every way Maxwell's 1865 brilliant perception of the real nature of light is abundantly justified; and for the first time we have a true theory of light, no longer based upon analogy with sound, nor upon a hypothetical jelly or elastic solid.
Light is an electro-magnetic disturbance of the ether. Optics is a branch of electricity. Outstanding problems in optics are being rapidly solved now that we have the means of definitely exciting light with a full perception of what we are doing and of the precise mode of its vibration.
It remains to find out how to shorten down the waves—to hurry up the vibration until the light becomes visible. Nothing is wanted but quicker modes of vibrations. Smaller oscillators must be used—very much smaller—oscillators not much bigger than molecules. In all probability—one may almost say certainly—ordinary light is the result of electric oscillation in the molecules of hot bodies, or sometimes of bodies not hot—as in the phenomenon of phosphorescence.
The direct generation ofvisiblelight by electric means, so soon as we have learnt how to attain the necessary frequency of vibration, will have most important practical consequences.
Speaking in this university, it is happily quite unnecessary for me to bespeak interest in a subject by any reference to possible practical applications. But any practical application of what I have dealt with this evening is apparently so far distant as to be free from any sordid gloss of competition and company promotion, and is interesting in itself as a matter of pure science.
For consider our present methods of making artificial light; they are both wasteful and ineffective.
We want a certain range of oscillation, between 7,000 and 4,000 billion vibrations per second; no other is useful to us, because no other has any effect upon our retina; but we do not know how to produce vibrations of this rate. We can produce a definite vibration of one or two hundred or thousand per second; in other words, we can excite a pure tone of definite pitch; and we can demand any desired range of such tones continuously by means of bellows and a keyboard. We can also (though the fact is less well known) excite momentarily definite ethereal vibrations of some million per second, as I have explained at length; but we do not at present seem to know how to maintain this rate quite continuously. To get much faster rates of vibration than this we have to fall back upon atoms. We know how to make atoms vibrate; it is done by what we call "heating" the substance, and if we could deal with individual atoms unhampered by others, it is possible that we might get a pure and simple mode of vibration from them. It is possible, but unlikely; for atoms, even when isolated, have a multitude of modes of vibration special to themselves, of which only a few are of practical use to us, and we do not know how to excite some without also the others. However,we do not at present even deal with individual atoms; we treat them crowded together in a compact mass, so that their modes of vibration are really infinite.
We take a lump of matter, say a carbon filament or a piece of quicklime, and by raising its temperature we impress upon its atoms higher and higher modes of vibration, not transmuting the lower into the higher, but superposing the higher upon the lower, until at length we get such rates of vibration as our retina is constructed for, and we are satisfied. But how wasteful and indirect and empirical is the process. We want a small range of rapid vibrations, and we know no better than to make the whole series leading up to them. It is as though, in order to sound some little shrill octave of pipes in an organ, we are obliged to depress every key and every pedal, and to blow a young hurricane.
I have purposely selected as examples the more perfect methods of obtaining artificial light, wherein the waste radiation is only useless and not noxious. But the old-fashioned plan was cruder even than this; it consisted simply in setting something burning; whereby not the fuel but the air was consumed, whereby also a most powerful radiation was produced, in the waste waves of which we were content to sit stewing, for the sake of the minute—almost infinitesimal—fraction of it which enabled us to see.
Every one knows now, however, that combustion is not a pleasant or healthy mode of obtaining light; but every one does not realize that neither is incandescence a satisfactory and unwasteful method which is likely to be practiced for more than a few decades, or perhaps a century.
Look at the furnaces and boilers of a great steam engine driving a group of dynamos, and estimate the energy expended; and then look at the incandescent filaments of the lamps excited by them, and estimate how much of their radiated energy is of real service to the eye. It will be as the energy of a pitch pipe to an entire orchestra.
It is not too much to say that a boy turning a handle could, if his energy were properly directed, produce quite as much real light as is produced by all this mass of mechanism and consumption of material. There might, perhaps, be something contrary to the laws of nature in thus hoping to get and utilize some specific kind of radiation without the rest, but Lord Rayleigh has shown in a short communication to the British Association at York that it is not so, and that, therefore, we have a right to try to do it.
We do not yet know how, it is true, but it is one of the things we have got to learn.
Any one looking at a common glow-worm must be struck with the fact that not by ordinary combustion, nor yet on the steam engine and dynamo principle, is that easy light produced. Very little waste radiation is there from phosphorescent things in general. Light of the kind able to affect the retina is directly emitted; and for this, for even a large supply of this, a modicum of energy suffices.
Solar radiation consists of waves of all sizes, it is true; but then solar radiation has innumerable things to do besides making things visible. The whole of its energy is useful. In artificial lighting nothing but light is desired; when heat is wanted it is best obtained separately by combustion. And so soon as we clearly recognize that light is an electric vibration, so soon shall we begin to beat about for some mode of exciting and maintaining an electrical vibration of any required degree of rapidity. When this has been accomplished the problem of artificial lighting will have been solved.
[1]
Being the general substance of a lecture to the Ashmolean Society in the University of Oxford, on Monday, June 3, 1889. [Reprinted from theLiverpool University College Magazine.]
[2]
Though, indeed, a century hence it may be premature to offer an opinion on such a point.
During the time when I was engaged in my preliminary medical studies—for I never admit to this day of being anything less than a medical student—the substance called ozone became the topic of much conversation and speculation. I cannot say that ozone was a discovery of that date, for in the early part of the century Von Marum had observed that when electrical discharges were made through oxygen in a glass cylinder inverted over water, the water rose in the cylinder as if something had either been taken away from the gas, or as if the gas itself had been condensed, and was therefore occupying a smaller space. It had also been observed by many electricians that during a passage of the electric spark through air or oxygen, there was a peculiar emanation or odor which some compared to fresh sea air, others to the air after a thunderstorm, when the sky has become very clear, the firmament blue, and the stars, if visible, extremely bright.
But it was not until the time, or about the time, of which I have spoken, 1846-49, that these discovered but unexplained phenomena received proper recognition. The distinguished physicist Schonbein first, if I may so say, isolated the substance which yielded the phenomena, and gave to it the name, by which it has since generally been known, ofozone, which means, to emit an odor; a name, I have always thought, not particularly happy, but which has become, practically, so fully recognized and understood, that it would be wrong now to disturb it.
Schonbein made ozone by the action of the electric spark on oxygen. He collected it, he tested its chemical properties, he announced it to be oxygen in a modified form, and he traced its action as an active oxidizer of various substances, and especially of organic substances, even when they were in a state of decomposition.
But Schonbein went further than this. He argued that ozone was a natural part of the atmosphere, and that in places where there was no decomposition, that is to say, in places away from great towns, ozone was present. On the high tower of a cathedral in a big city he discovered ozone; in the city, at the foot of the tower, he found no ozone at the same time. He argued, therefore, that the ozone above was used up in purifying the town below, and so suggested quite a new explanation of the purification of air.
The subject was very soon taken up by English observers, and I remember well a lecture upon it by Michael Faraday, in which that illustrious philosopher, confirming Schonbein, stated that he had discovered ozone freely on the Brighton Downs, and had found the evidence of it diminishing as he approached Brighton, until it was lost altogether in the town itself.
Such was the beginning of our knowledge of ozone, the precise nature of which has not yet been completely made out. At the present time it is held to be oxygen condensed. To use a chemical phrase, the molecule of oxygen, which in the ordinary state is composed of two atoms, is condensed, in ozone, as three atoms. By the electric spark discharged in dry oxygen as much as 15 per cent. may, under proper conditions, be turned into ozone. Ozone has also been found to be heavier than air. Professor Zinno says, that compared with an equal volume of air its density is equal to 1,658, and that it is forty-eight times heavier than hydrogen. Heat decomposes it; at the temperature of boiling water it begins to decompose. In water it is much less soluble than oxygen, and indeed is practically insoluble; when made to bubble through boiling water, it ceases to be ozone. The oxidizing power of ozone is very much greater than that of oxygen, and, according to Saret, when ozone is decomposed, one part of it enters into combination, the other remains simply as oxygen.
It is remarkable that some substances, like turpentine and cinnamon, absorb ozone and combine with it, a simple fact of much greater importance than has ever been attached to it. I found, for instance, that cinnamon which by exposure to the air has been made odorless and, as it is said, "spoiled," can be made to reabsorb ozone and gain a kind of freshness. It is certain also that some substances which are supposed to have disinfecting properties owe what virtues they possess to the presence of ozone.
On some grand scale ozone is formed in the air, and my former friend and colleague, the late Dr. Moffatt, of Hawarden, with whom I wrote a paper on "Meteorology and Disease," read before the Epidemiological Society in 1852-53, described what he designated ozone periods of the atmosphere, connecting these with storms. When the atmospheric pressure is decreasing, when with that there is increasing warmth and moisture, and when south and southwesterly winds prevail, then ozone is active; but when the atmospheric pressure is increasing, when the air is becoming dry and cold, and north and northeasterly winds prevail, then the presence of ozone is less active. These facts have also been put in another way, namely, that the maximum period of ozone occurs when there is greatest evaporation of water from the earth, and the minimum when there is greatest condensation of water on the earth; a theory which tallies well with the idea that ozone is most freely present when electricity is being produced, least present when electricity is in smallest quantity. Mr. Buchan, reporting on the observations of the Scottish Meteorological Society, records that ozone is most abundant from February to June, when the average amount is 6.0; and least from July to January, when the average is 5.7; the maximum, 6.2, being reached in May, and the minimum, 5.3, in November. This same excellent observer states that "ozone is more abundant on the sea coast than inland; in the west than the east of Great Britain; in elevated than in low situations; with southwest than with northeast winds; in the country than in towns; and on the windward than the leeward side of towns."
Recently a very singular hypothesis has been broached in regard to the blue color of the firmament and ozone. It has been observed that when a tube is filled with ozone, the light transmitted through it is of a blue color; from which fact it is assumed that the blue color of the sky is due to the presence of this body in the higher atmospheric strata. The hypothesis is in entire accord with the suggestion of Professor Dove, to which Moffatt always paid the greatest respect, viz., that the source of ozone for the whole of the planet is equatorial, and that the point of development of ozone is where the terrestrial atmosphere raised to its highest altitude, at the equator, expands out north and south in opposite directions toward the two poles, to return to the equator over the earth as the trade winds.
It is necessary for all who would understand the applications of ozone for any purpose, whether for bleaching purposes or pure chemical purposes, or for medical or sanitary purposes, to understand these preliminary facts concerning it, facts which bring me to the particular point to which I wish to refer to-day.
In my essay describing the model city, Hygeiopolis, it was suggested that in every town there should be a building like a gas house, in which ozone should be made and stored, and from which it should be dispensed to every street or house at pleasure. This suggestion was made as the final result of observations which had been going on since I first began to work at the subject in 1852. It occurred to me from the moment when I first made ozone by Schonbein's method, that the value of it in a hygienic point of view was incalculable.
To my then young and enthusiastic mind it seemed that in ozone we had a means of stopping all putrefaction, of destroying all infectious substances, and of actually commanding and destroying the causes which produced the great spreading diseases; and, although increase of years and greater experience have toned down the enthusiasm, I still believe that here one of the most useful fields for investigation remains almost unexplored.
In my first experiments I subjected decomposing blood to ozone, and found that the products of decomposition were instantly destroyed, and that the fluid was rendered odorless and sweet. I discovered that the red corpuscles of fresh blood decomposed ozone, and that coagulated blood underwent a degree of solution through its action. I put dead birds and pieces of animal substances that had undergone extreme decomposition into atmospheres containing ozone, and observed the rapidity with which the products of decomposition were neutralized and rendered harmless. I employed ozone medicinally, by having it inhaled by persons who were suffering from fœtor of the breath, and with remarkable success, and I began to employ it and have employed it ever since (that is to say, for thirty-seven years), for purposes of disinfection and deodorization, in close rooms, closets, and the like. I should have used it much more largely but for one circumstance, namely, the almost impracticable difficulty of making it with sufficient ease and in sufficient quantities to meet the necessities of sanitary practice. We are often obstructed in this way. We know of something exceedingly useful, but we cannot utilize it. This was the case with ozone. I hope now that difficulty is overcome. If it is, we shall start from this day on a new era in regard to ozone as an instrument of sanitation.
As we have seen, ozone was originally made by charging dry oxygen or common dry air with electricity from sparks or points. Afterward Faraday showed that it could be made by holding a warm glass rod in vapor of ether. Again he showed that it could be made by passing air over bright phosphorus half immersed in water. Then Siemens modified the electric process by inventing his well known ozone tube, which consists of a wide glass tube coated with tinfoil on its outside, and holding within it a smaller glass tube coated with tinfoil on its surface. When a current of dry air or oxygen was passed in current between these two tubes, and the electric spark from a Ruhmkorf coil was discharged by the terminal wires connected with tinfoil surfaces, ozone was freely produced, and this was no doubt the best method, for by means of a double-acting hand bellows currents of ozone could be driven over very freely. One of these tubes with hand bellows attached, which I have had in use for twenty-four years, is before the meeting, and answers as well as ever. The practical difficulty lies in the requirement of a battery, a large coil, and a separate bellows as well as the tube.
My dear and most distinguished friend, the late Professor Polli, of Milan, tried to overcome the difficulties arising from the use of the coil by making ozone chemically, namely, by the decomposition of permanganate of potassa with strong sulphuric acid. He placed the permanganate in glass vessels, moistened it gradually with the acid, and then allowed the ozone, which is formed, to diffuse into the air. In this way he endeavored, as I had done, to purify the air of rooms, especially those vitiated by the breaths of many people. When he visited me, not very long before his death, he was enthusiastic as to the success that must attend the utilization of ozone for purification, and when I expressed a practical doubt, he rallied me by saying I must not desert my own child. At the theater La Scala, on the occasion of an unusually full attendance, Polli collected the condensible part of the exhaled organic matter, by means of a large glass bell filled with ice and placed over the circular opening in the roof, which corresponds with the large central light. The deposit on this bell was liquid and had a mouldy smell; was for some few days limpid, but then became very thick and had a nauseous odor. When mixed with a solution of one part glucose to four parts of water, and kept at a temperature of from 20° to 24° C., this liquid underwent a slow fermentation, with the formation, on the superficies, of green must; during the same period of time, and placed under the same conditions, a similar glucose solution underwent no change whatever.
By the use of his ozone bottles Polli believed that he had supplied a means most suitable for directly destroying in the air miasmatic principles, without otherwise interfering with the respiratory functions. The ozonized air had neither a powerful nor an offensive smell, and it might be easily and economically made. The smell of ozone was scarcely perceptible, and was far less disagreeable than chlorine, bromine, and iodine, while it was more efficacious than either of these; if, therefore, its application as a purifier of a vitiated air succeeded, it would probably supply all the exigences of defective ventilation in crowded atmospheres. In confined places vessels might be placed containing mixtures of permanganate of potassa or soda and acid in proper quantities, and of which the duration of the action was known; or sulphuric acid could be dropped upon the permanganate.
This idea of applying ozone was no doubt very ingenious, and in the bottles before us on the table, which have been prepared in Hastings by Mr. Rossiter, we see it in operation. The disadvantages of the plan are that manipulation with strong sulphuric acid is never an agreeable or safe process, and that the ozone evolved cannot be on a large scale without considerable trouble.
In 1875 Dr. Lender published a process for the production of ozone. In this process he used equal parts of manganese, permanganate of potash, and oxalic acid. When this mixture is placed in contact with water, ozone is quickly generated. For a room of medium size two spoonfuls of this powder, placed in a dish and occasionally diluted with water, would besufficient. As the ozone is developed, it disinfects the surrounding air without producing cough.
Lender's process is very useful when ozone is wanted on a limited scale. We have some of it here prepared by Mr. Rossiter, and it answers exceedingly well; but it would be impossible to generate sufficient ozone by this plan for the large application that would be required should it come into general use. The process deserves to be remembered, and the physician may find it valuable as a means by which ozone may be medically applied, to wounds, or by inhalation when there are fœtid exhalations from the mouth or nostrils.
For the past ten or fifteen years the manufacture of ozone, for the reasons related above, has remained in abeyance, and it is to a new mode, which will, I trust, mark another stage of advancement, that I now wish to direct attention. Some years since, Mr. Wimshurst, a most able electrician, invented the electrical machine which goes by his name. The machine, as will be seen from the specimen of it on the table, looks something like the old electrical machine, but differs in that there is no friction, and that the plates of glass with their metal sectors, separated a little distance from each other, revolve, when the handle of the machine is turned, in opposite directions. The machine when it is in good working order (and it is very easily kept in good working order) produces electricity abundantly, and in working it I observed that ozone was so freely generated, that more than once the air of my laboratory became charged with ozone to an oppressive degree. The fact led me to use this machine for the production of ozone on a large scale, in the following way.
From the terminals of the machine two wires are carried and are conducted, by their terminals, to an ozone generator formed somewhat after the manner of Siemens', but with this difference, that the discharge is made through a series of fine points within the cylinders. The machine is placed on a table with theozone generator at the back of it, and can be so arranged that with the turning of the handle which works the machine a blast of air is carried through the generator. Thus by one action electricity is generated, sparks are discharged in the ozone generator, air is driven through, and ozone is delivered over freely.
If it be wished to use pure oxygen instead of common air, nothing more is required than to use compressed oxygen and to allow a gentle current to pass through the ozone generator in place of air. For this purpose Brin's compressed oxygen is the purest and best; but for ordinary service atmospheric air is sufficient.2
The advantages of this apparatus are as follows:
1. With care it is always ready for use, and as no battery is required nor anything more than the turning of a handle, any person can work it.
2. It can be readily moved about from one part of a room or ward to another part.
3. If required for the sick it can be wheeled near the bedside and, by a tube, the ozone it emits can be brought into action in any way desired by the physician.
I refer in the above to the minor uses of ozone by this method, but I should add that it admits of application on a much grander scale. It would now be quite easy in any public institution to have a room in which a large compound Wimshurst could be worked with a gas engine, and from which, with the additional apparatus named, ozone could be distributed at pleasure into any part of the building. On a still larger scale ozone could be supplied to towns by this method, as suggested in Hygeiopolis, the model city.
It will occur, I doubt not, to the learned president of this section, and to others of our common profession, that care will have to be taken in the application of ozone that it be used with discretion. This is true. It has been observed in regard to diseases, that in the presence of some diseases ozone is absent in the atmosphere, but that with other diseases ozone is present in abundance. During epidemics of cholera, ozone is at a minimum. During other epidemics, like influenza, it has been at a maximum. In our paper Dr. Moffatt and I classified diseases under both conditions, and the difference must never be forgotten, since in some diseases we might by the use of ozone do mischief instead of good. Moreover, as my published experiments have shown, prolonged inhalation of ozone produces headache, coryza, soreness of the eyes, soreness of the throat, general malaise, and all the symptoms of severe influenza cold. Warm-blooded animals, also, exposed to it in full charge, suffer from congestion of the lungs, which may prove rapidly fatal. With care, however, these dangers are easily avoided, the point of practice being never to charge the air with ozone too abundantly or too long.
A simple test affords good evidence as to presence of ozone. If into twenty ounces of water there be put one ounce of starch and forty grains of potassium iodide, and the whole be boiled together, a starch will be made which can be used as a test for ozone. If ozone be passed through this starch the potassium is oxidized, and the iodine, set free, strikes a blue color with the starch. Or bibulous paper can be dipped in the starch, dried and cut into slips, and these slips being placed in the air will indicate when ozone is present. In disinfecting or purifying the air of a room with ozone, there is no occasion to stop until the test paper, by change of color, shows that the ozone has done its work of destroying the organic matter which is the cause of impurity or danger. For my own part, I have never seen the slightest risk from the use of ozone in an impure air. The difficulty has always been to obtain sufficient ozone to remove the impurity, and it is this difficulty which I hope now to have conquered.—The Asclepiad.
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