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. The luminiferous ether 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 = a sin (p t - n x),

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—elasticity and inertia. 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 aurorae; 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 of visible light 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.

* * * * *



ON PURIFICATION OF AIR BY OZONE—WITH AN ACCOUNT OF A NEW METHOD.[1]

[Footnote 1: Paper read in Section C, Domestic Health, at the Hastings Health Congress, on Friday, May 3, 1889.]

By Dr. B. W. RICHARDSON.

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, of ozone, 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 foetor 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 deg. to 24 deg. 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 be sufficient. 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 foetid exhalations from the mouth or nostrils.

A NEW METHOD.

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 the ozone 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]

[Footnote 2: For illustration to-day, Messrs Mayfield, the electrical engineers of Queen Victoria Street, E. C., have been good enough to lend me a machine fitted up on the plan named. It works so effectively that I can make the ozone given off from it detectable in every part of this large hall.]

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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HEAT IN MAN.

At a recent meeting of the Physiological Society of Berlin, Prof. Zuntz spoke on heat regulation in man, basing his remarks on experiments made by Dr. Loewy. The store of heat in the human body at any one time is very large, equal, in fact, to nearly all the heat produced by the body during twenty hours, hence the heat given off to a calorimeter during a given period cannot be taken as a measure of the heat production. This determination must be based rather upon the amount of oxygen consumed and of carbonic acid gas given off. The purpose of the experiments was to ascertain what alteration the gaseous interchange of the body undergoes by the application of cold, inasmuch as existing data on this point are largely contradictory.

The observations were made on a number of men whose respiratory gases were compared, during complete rest, when they were at one time clothed, at another time naked, at temperatures from 12 deg. to 15 deg. C., and in warm and cold baths. Each experiment lasted from half an hour to an hour, during which period the gases were repeatedly analyzed. As a result of fifty-five experiments, twenty showed no alteration of oxygen consumption as the result of cooling, nine gave a lessened consumption, while the remaining twenty-six showed an increased using up of oxygen. This diversity of result is explicable on the basis of observations made by Prof. Zuntz, who was himself experimented upon, as to his subjective heat sensations during the experiments. He found that after the first impression due to the application of cold is overcome, it was quite easy to maintain himself in a perfectly passive condition; subsequently it required a distinct effort of the will to refrain from shivering and throwing the muscles into activity, and finally even this became no longer possible, and involuntary shivering and muscular contraction supervened, as soon as the body temperature (in ano) had fallen 1/2 deg. to 1 deg. C. During the first stage of cooling, Zuntz's oxygen consumption showed a uniform diminution; during the period also in which shivering was repressed by an effort of the will, cooling led to no increased consumption of oxygen, but as soon as shivering became involuntary there was at once an increased using up of oxygen and excretion of carbonic acid.

This explains the differences in the results of Dr. Loewy's experiments, and may be taken to show that in man, and presumably in large animals, heat regulation as directly dependent upon alteration (fall) in temperature of the surrounding medium does not exist; the increased heat production is rather the outcome of the movements resulting from the application of cold to the body. In small animals, on the other hand, there undoubtedly exists a heat regulation dependent upon an increased activity of chemical changes in the tissues set up by the application of cold to the surface of the body, and in this case the thermotaxic centers in the brain most probably play some part.—Dr. Herter gave an account of experiments made by Dr. Popoff on the artificial digestion of various and variously cooked meats. Lean beef and the flesh of eels and flounders were digested in artificial gastric juice; the amount of raw flesh thus peptonized was in all cases greater than that of cooked meat similarly treated. The flesh was shredded and heated by steam to 100 deg. C. The result was the same for beef as for fish. When compared with each other, beef was, on the whole, the most digestible, but the amount of fish flesh which was peptonized was sufficiently great to do away with the evil repute which fish still has in Germany as a proteid food. Smoked meat differed in no essential extent from raw meat as regards its digestibility.

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PRESERVATION OF SPIDERS FOR THE CABINET.

For several years past, I have devoted a portion of my leisure time to the arrangement of the collection of Arachnidae of the Natural History Museum of the University of Gand. This collection, which is partially a result of my own captures, is quite a large one, for a university museum, since it comprises more than six hundred European and foreign specimens. Each group of individuals of the small forms and each individual of the large forms is contained in a bottle of alcohol closed with a ground glass stopper, and, whenever possible, the specimens have been spread out and fixed upon strips of glass.

The loss of alcohol through evaporation is almost entirely prevented by paraffining the stoppers and tying a piece of bladder over them.

Properly labeled, the series has a very satisfactory aspect, and is easily consulted for study. The reader, however, will readily understand how much time and patience such work requires, and can easily imagine how great an amount of space the collection occupies, it being at least twenty times greater than that that would be taken up by a collection of an equal number of insects mounted in the ordinary way on pins and kept in boxes.

These inconveniences led me to endeavor to find out whether there was not some way of preserving spiders, properly so called, in a dry state, and without distortion or notable modification of their colors.

Experience long ago taught me that pure and simple desiccation, after a more or less prolonged immersion in alcohol, gives passable results only with scorpions, galeodes, phrynes, and mygales, and consequently with arachnides having thick integuments, while it is entirely unsuccessful with most of the spiders. The abdomen of these shrivels, the characteristic colors disappear in great part, and the animals become unrecognizable.

Something else was therefore necessary, and I thought of carbolated glycerine. My process, which I have tried only upon the common species of the country—Tegenaria domestica, Epeira cucurbitina, Zilla inclinata, etc., having furnished me with preparations that were generally satisfactory. I think I shall be doing collectors a service by publishing it in the Naturaliste.

The specimens should first be deprived of moisture, that is to say, they should be allowed to remain eight or ten days in succession in 50 per cent. alcohol and in pure commercial alcohol. Absolute alcohol is not necessary.

After being taken from the alcohol, and allowed to drain, the specimens are immersed in a mixture compound of

Pure glycerine 2 volumes, Pure carbolic acid in crystals 1 volume.

In this they ought to remain at least a week, but there will be no harm if they are left therein indefinitely, so that the collections of summer may be mounted during winter evenings.

What follows is a little more delicate, although very easy. After being removed from the carbolated glycerine, the spiders are placed upon several folds of white filtering paper, and are changed from time to time until the greatest part of the liquid has been absorbed. An insect pin is then passed through the cephalothorax of each individual and is inserted in the support upon which the final desiccation is to take place. This support consists of a piece of sheet cork tacked or glued at the edges to a piece of wood at least one inch in thickness. Upon the cork are placed four or five folds of filtering paper, so that the ventral surface of the pinned spider is in contact with this absorbing surface. For the rest, the legs, palpi, spinnerets, etc., are spread out by means of fine pins, precisely as would be done in the case of coleoptera.



The setting board is put for two or three months in a very dry place under cover from dust.

The spiders thus treated will scarcely have changed in appearance, the abdomen of the largest Epeiras will have preserved its form, the hairs will in nowise have become agglutinated, and a person would never suspect that glycerine had performed the role.

The forms with a large abdomen require a special precaution; it is necessary to pass the mounting pin through a piece of thin cardboard or of gelatine prolonged behind under the abdomen, because the latter is heavy, and the pedicel that connects it with the cephalothorax easily breaks.

The specimens are mounted in boxes lined with cork, just as insects are.

As there is nothing simpler than to have in one's laboratory three bottles, two of them containing alcohol and the other containing carbolated glycerine, and as it is easy to make setting boards capable of holding from twenty to thirty individuals at once, it will be seen that, with a little practice, the method is scarcely any more complicated than the one daily employed for coleoptera and orthoptera, which latter, too, must pass through alcohol, and be pinned, spread out, and dried. There are but two additional elements, carbolated glycerine and absorbent paper. I do not estimate the time necessary for desiccation as being very long, since the zoologist can occupy himself with other subjects while the specimens are drying. Let us add that the process renders the preservation indefinite, and that destructive insects are not to be feared. Some vertebrates, such as monkeys, that I preserved in the flesh ten years ago, by a nearly identical method, are still intact.—F. Plateau, in Le Naturaliste.

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DRIED WINE GRAPES.

According to a report of the Committee of the Grape Growers' and Wine Maker's Association of California, the drying of wine grapes on a large scale was begun during the vintage season of 1887, in which season about eight carloads in all were made and sold, the bulk of which came from the vicinity of Fresno; that year, the committee are informed, the growers netted about three and a half cents per pound. During the season of 1888 about 112 carloads were dried, packed, and sold, netting the growers from two and a half to three and a half cents per pound, depending on the quality of the fruit. The great bulk of that year's product has entered into consumption, but there yet remains unsold to consumers, we are informed, about ten carloads, which, it is expected, will be sold during the next three months. It has been observed by those handling this product that the largest sales of dried wine grapes in 1888 and 1889 took place at those points to which the first lots were shipped in 1887, which would show that as the product becomes better known it finds a readier market.

Dried wine grapes are prepared in a similar manner to raisins; that is they are dried in the sun, but do not require the same care in handling that are given to raisins. Wooden trays 2 x 3 are sometimes used, but it is by no means necessary to go to the expense of procuring trays, as it has been found that a good quality of coarse brown paper will answer every purpose, and this, with care, may be made to last two or three seasons. The drying was last season principally done on the bare ground, but there is much loss by shelling, as those dried are required to be turned; a pitchfork is used for that purpose. Brown building paper can be procured of city paper dealers in large rolls at four and a half cents per pound; according to the thickness, it will cost from one and three-quarters to three and a half cents per square yard. A thin, tough, waterproof paper is also made in rolls at about six cents a square yard. Wine grapes dry in from ten days to three weeks, according to variety and weather, and with the exception of Malvoisie, Rose of Peru, and Black Hamburg, from three and a half to four and a half tons of the green fruit are required to make one of the dried; these three varieties, however, being large, meaty, and a firm pulp, do not require more than from three to three and a half tons of the green fruit to produce one ton of dried, and are, therefore, the most profitable for drying; they also command better values in the market. The grapes are sufficiently dried when, on being rolled between the thumb and finger, no moisture exudes, and also when the stems are found to be dry and brittle, so that they can be separated readily from the berries. After the grapes have reached the proper state of dryness, they are taken in boxes or sacks to the packing house, where they are stemmed and cleaned, after which they are packed in white cotton sacks, holding from fifty to seventy-five pounds each, and when marked are ready for shipment.

The stemming and cleaning of the dried grapes is done by special machines designed for that purpose, which leaves the fruit in a bright, clean condition attractive to purchasers. These machines are at present built only by James Porteous, Fresno, and are operated either by hand or power. The cost of a stemmer and cleaner complete is $80, f. o. b. cars at Fresno. Where several producers can do so, it would be advisable to club together and get the machine in this way. Much extra expense could be avoided and one set of machinery would serve several vineyards, possibly an entire district where time was not a great object; or some one person in a district could purchase an outfit and do the work by contract, going from place to place. The capacity of the stemmer and cleaner is from five to eight tons per day, when the grapes are in proper condition; and the cost or charge for stemming, cleaning, sacking, and sewing up the sacks is from four to five dollars per ton when the producer furnishes the sacks. Good cotton sacks, holding about seventy-five pounds, cost from eight to ten cents each, including the necessary twine. Last year dried grapes were generally sold for cash, f. o. b., but it is probable that other markets could be secured by selling on consignment.

As to the advisability of such a course, each producer must himself be the judge. It is, however, quite certain that until consumers have an opportunity to try this product, the sales will necessarily be more or less limited, unless vigorously pushed by merchants and others interested in extending the markets for California products in the Eastern cities not yet tried. The varieties most suitable and profitable for drying, and especially for consumption in the Eastern markets, are the Malvoisie, Rose of Peru, Black Hamburg, Mission, Zinfandel, Charbono, Grenache, and in some localities the Carignan, of the dark varieties, and the Feher Zagos and Golden Chasselas of the white grapes; there are many other white grapes that are excellent when dried, but are too valuable for wine-making purposes, or are too small or deficient in sugar for use as dried grapes.

The same is true of the dark grapes, some of which ripen so late that it would be impossible to dry them in the sun, and the use of artificial heat is, at present prices, too expensive. Therefore, the varieties mentioned, which generally mature early, are found to be the most suitable for this purpose. This product is sold by dealers in the Eastern cities for cooking purposes, and as a substitute for dried fruits, such as peaches, apples, apricots, etc., in comparison with which it is usually much cheaper; while for stewing and for puddings and pies it answers the same purpose. The demand for this product will probably be gauged by the Eastern fruit crop; that is, the quantity that can be disposed of will depend upon the quantity of Eastern fruit in the market, and the prices will be largely dependent upon that of dried fruit.

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WALNUT OIL.

By THOMAS T. P. BRUCE WARREN.

This oil, which I obtained from the fully ripened nut of the Jugluns regia, has so many excellent properties, especially for mixing with artists' colors for fine art work, that I am surprised at the small amount of information available on this interesting oil.

Walnut oil is largely used for adulterating olive oil, and to compensate for its high iodine absorption it is mixed with pure lard oil olein, which also retards the thickening effect due to oxidation. The marc left on expression of the oil is said to be largely used in the manufacture of chocolate. Many people, I am told, prefer walnut oil to olive oil for cooking purposes.

The value of this oil for out-door work has been given me by a friend who used it for painting the verandas and jalousies of his house (near Como, Italy) some twenty years ago, and which have not required painting since. In this country, at least, walnut oil is beyond the reach of the general painter, and I do not know that the pure oil is to be obtained as a commercial article, even on a small scale.

It was in examining the properties of this and other oils, used as adulterants of olive oil, that I was obliged to prepare them so as to be sure of getting them in a reliable condition as regards purity. The walnuts were harvested in the autumn of 1887, and kept in a dry airy room until the following March. The kernels had shrunk up and contracted a disagreeable acrid taste, so familiar with old olive oil in which this has been used as an adulterant. Most oxidized oils, especially cotton seed oil, reveal a similar acrid taste, but walnut oil has, in addition, an unmistakable increase in viscosity. The nuts were opened and the kernels thrown into warm water, so as to loosen the epidermis; they were then rubbed in a coarse towel, so as to blanch them. The decorticated nuts were wiped dry and rubbed to a smooth paste in a marble mortar. The paste was first digested in CS2, then placed in a percolator and exhausted with the same solvent, which was evaporated off. The yield of oil was small, but probably, if the nuts had been left to fully ripen on the trees without knocking them off, the yield might have been greater. It is by no means improbable that oxidation may have rendered a portion of the oil insoluble. The decorticated kernels gave a perfectly sweet, inodorous, and almost colorless oil, which rapidly thickens to an almost colorless, transparent, and perfectly elastic skin or film, which does not darken or crack easily by age. These are properties which, for fine art painting, might be of great value in preserving the tinctorial purity and freshness of pigments.

Sulphur chloride gives a perfectly white product with the fresh oil, but, when oxidized, the product is very dark, almost black. The iodine absorption of the fresh oil thus obtained is very high, but falls rapidly by oxidation or blowing. A curious fact has been disclosed with reference to the oxidation of this and similar oils. If such an oil be mixed with lard oil, olive oil, or sperm oil, it thickens by oxidation, but is perfectly soluble. Such a mixture is largely used in weaving or spinning. Commercial samples of linseed oil, when cold-drawn, have a much higher iodine absorption, probably due to the same cause. Oils extracted by CS2 are very much higher than the same oils, especially if hot-pressed.—Chem. News.

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THE PYRO DEVELOPER WITH METABISULPHITE OF POTASH.

By Dr. J. M. EDER.

Lately I called attention to the metabisulphite of potassium as an addition to the pyro solution for development, and can give now some of my experiences with this salt.

The metabisulphite of potassium, which was introduced into the market by Dr. Schuchardt, and whose correct analysis is not known yet, is a white crystal, which in a solid condition, as well as in an aqueous solution, has a strong smell of sulphurous acid. An aqueous 2 per cent. solution of this salt dissolves pyrogallic acid to a weak yellowish color, being distinguished from the more light brown solution of sulphite of soda and pyro. The solution kept very well for four weeks in half-filled bottles, and showed a better preservation than the usual solution of pyro and sulphite of soda. More than 2 per cent. of the metabisulphite of potassium is without any advantage. If this solution is mixed with soda, a picture will develop rapidly, but the same will show a strongly yellow coloration in the gelatine film. Sulphite of soda has to be added to the soda solution to obtain an agreeable brownish or black tone in the negatives.

If the contents of metabisulphite and pyro-soda developer are increased, it will act very slowly; larger quantities of the metabisulphite of potassium, therefore, act like a strong retarder. In small quantities there is no injurious retarding action, but it will have the effect that the plates obtain very clear shadows in this developer, and that the picture appears slower, and will strengthen more slowly. The strongly retarding action of larger quantities of metabisulphite might be accounted for in that the bisulphite will give, with the carbonate of soda, monosulphite and soda bicarbonate, which latter is not a strong enough alkali to develop the bromide of silver strongly with pyro. An increase of soda compensates this retarding action of the metabisulphite of potassium.

Good results were obtained by me with this salt after several tests, by producing the following solutions:

A.

Pyrogallic acid 4 grammes. Metabisulphite of potassium 11/2 " Water 100 c. c.

This solution keeps for weeks in corked bottles.

B.

Crystallized soda 10 grammes. Neutral sulphite of soda 15 " Water 100 c. c.

Before using mix—

Pyro solution A 20 c. c. Soda solution B 20 " Water 20 "

The developer acts about one and a half times slower than the ordinary pyro soda developer, approaching to the latter pretty nearly, and gives to the negatives an agreeable color and softness, with clear shadows. If the negatives are to be thinner, more water, say 30 to 40 c. c., is taken. If denser, then the soda is increased, and the water in the developer is reduced. An alum bath before fixing is to be recommended.

An advantage of this development is the great durability of the pyro-meta sulphite solution. The cost price is about the same as that of the ordinary pyro developer. At all events, it is worth while to make further investigation with the metabisulphite of potassium, the same being also a good preservative for hydroquinone solutions.—Photographische Correspondenz; Reported in the Photo. News.

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