Now if a conductor, or coil of wire, be placed in the field across the direction of a magnetic needle, and the field be varied either by varying the current or moving the magnet, a current will be developed in the conductor. It is impossible at this distance to appreciate the interest excited by the announcement of this principle, not only among scientists, but also among inventors and those who saw practical possibilities for the future; and probably no one more fully appreciated its value than Faraday himself. Yet he made no effort to develop it further, or even to protect his interest by a patent, as is common in these days. He was eminently a scientist, and this was his free gift to the world. He said: "I have rather been desirous of discovering new facts and relations than of exalting those already obtained, being a.s.sured the latter would find their full development hereafter."

Among the first to attempt successfully to exalt the new discovery was Pixii, an instrument maker of Paris, in 1832. He wound two coils of very fine insulated wire upon the ends of a piece of soft iron, bent in a horseshoe form. A permanent horseshoe magnet was then placed with poles very close to the ends of the iron in the coils. The field so produced was then rapidly varied by revolving the magnet on an axis parallel to its length. The soft iron cores of the coils became strongly magnetized as the poles of the revolving magnet came opposite to them; and their polarity was reversed at each half-revolution of the magnet. By this plan currents of considerable intensity and alternating in direction at each revolution were induced in the coil.

The ends of the coil were next connected to the external circuit through a "commutator." This is a device which is arranged to convert the alternating current of the coils into a current of one direction in the external circuit, and which in some form is found on all direct-current dynamos. Joseph Saxton, an American, improved upon Pixii's machine by rotating the coils, or armature as it is called, and making the heavier magnet stationary. The essential points of construction being worked out, improvements followed rapidly. Dr.

Werner Siemans, of Berlin, introduced an important modification by making the revolving armature of a cylinder of soft iron, having a groove cut throughout its length on opposite sides. In these grooves a wire was wound and the armature was rotated on its axis between the poles of several magnets.

In all the earlier machines permanent magnets of steel were used. The next important step was to use electro-magnets of soft iron, excited by a current flowing through many turns of wire wound around the legs of the magnet. These could be made much more strongly magnetic than the permanent magnets. The exciting current was at first obtained from a small permanent magneto machine; but it was afterward found that the machine could be made self-exciting. Soft-iron electro-magnets, after being once magnetized, remain slightly magnetic. This will produce a weak current in the revolving armature which is turned into the magnet coils. The magnets are thus further magnetized, and again react upon the armature with greater intensity. In this way a _strong_ current is rapidly built up, and after wholly or in part pa.s.sing around the magnet coils to sustain its magnetism, can be carried out into the circuit to serve the great variety of purposes to which it is now put.

The essential points in the evolution of the dynamo can here be sketched only in broadest outline. Even to catalogue in detail, the improvements of Edison and Brush, Gramme and Wheatstone, and a host of others who have contributed to the work, would require a volume. One fact, however, should ever be kept in mind: Whatever may be the extent of the superstructure of electrical science, it is all built upon the foundation of electro-magnetic induction laid by Michael Faraday. The little "magnetic spark" he first produced, and the trembling of his galvanometer-needle, were but signals of the birth of the giant of the century.

These are the days of electricity and steel, and a fitting part of the intense age in which they exist. That we have as yet seen but a partial development of the possibilities of the electrical discovery, no one can doubt. The rush of the trolley car, and the blinding flash of the electric light, are but challenges thrown out to the future for even greater achievements. That they will come no one will question; but where is the daring prophet who will hazard a guess as to what they will be?

THE UNKNOWN RAY AND ENTOGRAPHY.

It is difficult to name the unknown. In the ancient world all the unknown was included in the idea of G.o.d. It remained for the evangelist to declare that G.o.d is a _spirit_--thus separating the natural forces of the material world from the Supreme Power who is from eternity.

This century has been the epoch of investigation into the nature of the imponderable forces. Sound and light and heat have been known as the princ.i.p.al agents of sensation since the first ages of man-life on the earth; but their nature has not been well understood until within the memories of men still living. Electricity was also vaguely known--but very indistinctly--from ancient times. It has remained for the scientific investigators of our age to enter into the secret parts of nature and lay bare to the understanding many of the hitherto unknown facts relating to the imponderable agents.

The laws of heat, of acoustics, of light, have been clearly arranged and taught; but they have not been placed beyond the reach of new interpretation and possibly not beyond the reach of complete revolution and reconstruction. That which has been accepted as definitely known with regard to these agents has now to be reviewed, and possibly to be learned over again from first principles.

As to electricity in its various forms and manifestations, that sublime and powerful agent began to be better known just before the middle of the century. Since that time there has been almost constant progress in the science of this great force, until at the present time it is handled, controlled and understood in its phenomena almost as easily as water is poured into a vessel, air compressed under a piston, or hydrogen made to inflate a balloon.

It has remained, however, for the last half decade of the great century to come upon and investigate a hitherto unknown force in nature. Certain it is that the new force exists, that it is everywhere, that it is a part of the profound agency by which life is administered, that its control is possible, and that its probable applications are as wonderful--perhaps more wonderful--than anything ever hitherto discovered by scientific investigation.

It is not unlikely that since the day, or evening, on which Galileo, with his little extemporized telescope, out in the garden of the Quirinal, at Rome, compelled bigotry to behold the shining horns of the crescent Venus, thus opening as if by compulsion the sublime vista of the heavens and bringing in a new concept of the planetary and stellar worlds,--no such other discovery as that of the so-called Rontgen rays has been made. The results which seem likely to flow from this marvelous revelation surpa.s.s the human imagination. Let us try in a few words to realize the discovery, and define what it is.

It was on the eighth of November, 1895, that Dr. William Konrad Rontgen, of Wurzburg, made the discovery which seems likely to contribute so much to our knowledge of the mysterious processes of nature. On that day Dr. Rontgen was working with a Crookes tube in his laboratory. This piece of apparatus is well known to students and partly known to general readers. It consists of a gla.s.s cylinder, elongated into tubular form, and hermetically closed at the ends. When the tube is made, the air is exhausted as nearly as possible from it, and the ends are sealed over a vacuum as perfect as science is able to produce. Through the two ends, bits of platinum wire are pa.s.sed at the time of sealing, so that they project a little within and without. The interior of the tube is thus a vacuum into which at the two ends platinum wires extend. Electrical communication with outside apparatus is thus supplied.

It has long been known that on the discharge of an electrical current into this kind of vacuum peculiar and interesting phenomena are produced. The platinum wires at the two ends are connected with the positive and negative wires or terminals of an induction coil. When this is done, the electrical current discharged into the vacuum seems to flash out around the inner surfaces of the tube, in the form of light. There are brilliant coruscations from one end to the other of the tube. The tips of the platinum wire const.i.tuting the inner poles glow and seem to flame. That pole which is connected with the positive side of the battery is called the _anode_, or _upper_ pole, and that which is connected with the negative, or receptive, side of the battery, is called the _cathode_, or lower pole. It was in his experimentation with this apparatus, and in particular in noticing the results at the cathode or lower end of the tube, that Professor Rontgen made his famous discovery. It was for this reason that the name of "cathode rays" has been given to the new radiant force; but Dr. Rontgen himself called the phenomena the X, or unknown, rays.

In the experimentation referred to, Rontgen had covered the gla.s.s tube at the end with a shield of black cardboard. This rendered the glow at the cathode pole completely invisible. It chanced that a piece of paper treated with platino-barium cyanide for photographic uses was on a bench near by. Notwithstanding the fact that the tube was covered with an opaque shield, so that no _light_ could be transmitted, Professor Rontgen noticed that changes in the barium paper were taking place, _as though_ it were exposed to the action of light! Black lines appeared on the paper, showing that the surface was undergoing chemical change from the action of some invisible and hitherto unknown force!

This was the moment of discovery. The philosopher began experimenting.

He repeated what had been accidentally done and was immediately convinced that a force, or, as it were, invisible rays were streaming from the cathode pole of the tube through the gla.s.s, and through a substance absolutely opaque, and that these rays were performing their work at a distance on the surface of paper that was ordinarily sensitive only to the action of light.

Certain it was that _something_ was doing this work. Certain it was that it was _not light_. Highly probable it was that it was not any form of _electricity_, for gla.s.s is impermeable to the electrical current. Certain it was that it was _not sound_, for there was no noise or atmospheric agitation to produce such a result. In a word, it was demonstrated then and there that a hitherto unknown, subtle and powerful agent had been discovered, the applications of which might be of almost infinite range and interest.

Professor Rontgen soon announced his discovery to the Physico-Medical Society of Wurzburg. It was at the December meeting of this body that the new stage in human progress was declared. The news was soon flashed all over the world, and scientific men in every civilized country began at once to experiment with the cathode light--if light that might be called that lighted nothing.

In Rontgen's announcement he stated that there had been by the scientists Hertz and Lenard, in 1894, certain antecedent discoveries from which his own might in some sense be deduced. There was, however, a great difference between the discovery made by Rontgen and anything that had preceded it. His stage of progress in knowledge was this, that during the discharge of _one_ kind of rays of force from the cathode pole in a Crookes tube _another kind_ of rays are set free, which differ totally in their nature and effects from anything hitherto known. It is this fact which has indissolubly connected the name of Konrad Rontgen with that great bound in scientific knowledge which seems likely to modify nearly all the other scientific knowledge of mankind.

Everywhere, in the first months of 1896, the experimenters went to work to verify and apply the discovery of the German philosopher. It was at once discerned that the new force, since it would freely traverse opaque bodies and produce afterward chemical changes on sensitized surfaces similar to those ordinarily produced _by_ light, might be used for delineating (we can hardly say _photo_ graphing) the interior outlines and structure of opaque bodies!

On this line of experimentation the work at once began, and with remarkable success. Rontgen himself was the first man in the world to obtain, as _if_ by photography, the invisible outline of objects through opaque materials. He soon obtained a delineation of the bones of a living hand through the flesh, which was only dimly traced in the resulting picture. In like manner coins were delineated through the leather of pocketbooks. Other objects were pictured through intervening plates of metal or boards of wood. The possibility of discovering the visible character of invisible things, and even _of seeing directly through_ opaque materials into parts where neither light nor electricity can penetrate, was fully shown.

The work of picture taking in the interior of bodies and through opaque materials was quickly taken up by philosophers in England, France and the United States. Almost everywhere the physical laboratories witnessed daily this form of experimentation. Swinton, of London; Robb, of Trinity College, Dublin; Morton, of New York; Wright, of Yale University, and in particular Thomas A. Edison, of Menlo Park, attacked the new problem with scientific zeal, and with startling results. It remained for Edison to discover that the new force acted in some respects in the manner of _sound_ rather than in the manner of _light_. Thus, for example, he showed that the invisible rays not only _pa.s.s through_ substances that are opaque to light and non-conductors of electricity, but that the invisible rays _run around the edges and sides_ of plates, then proceeding on their way somewhat in the manner of sound. A sound made on one side of a metallic plate is heard on the other side _partly_ by transmission through the plate, and _partly_ by going around the edges, by atmospheric transmission. The new force rays act in this manner, and Edison is said to have procured pictures by means of the invisible agent while it was _going around the corner _ of an opaque obstruction!

The pre-eminence of Thomas A. Edison as a scientific explorer and inventor depends upon a quality of mind which enables him more easily than others--more distinctly than any others--to see the touch of each new discovery with existing conditions, and the application of it to the problems of life. Edison catches the premonitory spark struck in the darkness by some other master's hammer, and with that kindles a conflagration. Though not the discoverer of the Rontgen ray, he was able, as it would appear, to understand that discovery better even than the discoverer. He almost immediately applied the new increment of knowledge more successfully, we think, than any contemporary scientist. His experimentation led him directly to the discovery of the important fact that no photographic apparatus of any kind is needed to enable an observer to use the X-rays in the delineation or inspection of objects through opaque substances. He said within himself: "Why not pa.s.s the X-rays through the object to be inspected and then convert them into visibility, as if by fluorescence."

This scientific question Edison almost immediately solved.

Fluorescence is a property which some transparent bodies have of producing, either on their surface or within their substance, light different in color from that of its origin. This happens, for example, when _green_ crystals of fluor spar afford _blue_ reflections of light. Gla.s.s may be rendered fluorescent, as is seen in the Geisler and Crookes tubes. Edison conceived the project of using this phenomenon to get back the invisible rays into visibility.

The substance which he employed was the tungstate of calcium. Taking crystals of this chemical compound, he spread the same over a cloth or paper screen, and used that screen to catch and convert the invisible images carried against it by the X-rays. To his surprise, his experiment was completely successful. All that is needed in this case is the cathode light, the object to be examined (as for instance the hand), and the screen treated with tungstate of calcium. The observer looks through the screen, or into it, and sees _with the unaided eye_ the invisible interior parts of the object examined, held between the screen and the cathode light. The invisible rays take the image of the interior parts of an opaque object, and carry that image to the screen, where it is reconverted into visibility and delivered to the eye of the observer, without the aid of any instrument at all! It is on this simple principle that Edison has invented his surgical and physiological lamp. The announcement is that with this lamp the surgeon may look through the calcium tungstate screen and examine, for example, the fractured bones of the hand, and set them perfectly by actual inspection of the parts with his eye!

What then _is_ the cathode ray? At the present time its nature is not understood. That it is a form or mode of motion goes with the saying--unless it should be presently shown that all the imponderable forces are really _material_ in their nature; that is, that they are an inconceivably fine and attenuated form of matter in varying manifestations.

The cathode rays are not light. They are not sound. They are not electricity or magnetism. They are not heat. They are not any of the known forms of force. They seem to be a new transformation of some one or more of the known agents. It has long been observed that _motion_ is accompanied with _sound_, and that motion also, if increased, becomes manifest in _heat_. It is known that heat is convertible into light, and light into electricity.

It is possible that at the bottom of all these phenomena lies the force of gravitation. This force is absolute and universal. All the others are partial and limited. All the others, even the newly discovered cathode rays, are subject to obstruction by certain forms of matter; that is, to them certain forms of matter are opaque. But gravitation knows no opacity in the universe. No atom of matter is exempt from its sway. It streams through all obstructive media as though such media did not exist. It would appear that heat, light, electricity, sound, the cathode rays, and all other forms of force in nature are probably variations, and as it were limited expressions and manifestations, of _the one supreme force_ that supports the const.i.tution of the physical universe; and that one supreme force is _gravitation_!

Stages in Biological Inquiry.

THE NEW INOCULATION.

Any account of the scientific progress of this century which omits the name of Louis Pasteur would be lamentably incomplete. In that part of science which relates strictly to human life and the means of preserving it, the work of this great man must be placed in the first rank. Indeed, we believe that no other stride in biological investigation from the beginning of time has been so great in its immediate and prospective results as has been the increment contributed by Pasteur and his contemporary Koch. The success of these two experimental philosophers grew out of the subst.i.tution of a new theory for one that had hitherto prevailed respecting some of the fundamental processes in living matter.

Up to about the close of the third quarter of this century, the belief continued to prevail in the possibility of the propagation and production of germ life without other germ life to precede it. It was held that fermentation is not dependent upon living organisms, and that fermentation may be excited in substances from which all living germs have been excluded. This belief led to the theory of _abiogenesis_ so-called--a term signifying the production of life without life to begin with.

The question involved in this theory was hotly debated by philosophers and scientists in the Sixties and Seventies. The first great work of Pasteur in biological investigation was his successful demonstration of the impossibility of spontaneous generation. About 1870, he became a careful experimenter with the phenomena of fermentation. As his work proceeded, he was more convinced that fermentation can never occur in the absence and exclusion of living germs; and this view of the deep-down processes in living matter has now been accepted as correct.

The next stage in the work of Pasteur was the discovery that certain substances, such as glycerine, are products of fermentation. From this foundation firmly established he pa.s.sed on to consider the phenomena of disease. He had been, in the first place, a teacher in a normal school at Paris. In 1863, when he was thirty-nine years of age, he was a professor of geology. Afterward he had a chair of chemistry at the Sorbonne. In 1856 we find him experimenting with light, and after that he turned to biological investigations. This led him to the results mentioned above, and presently to the discovery that the contagious and infectious diseases with which men and the lower animals are affected are in general the results of processes in the system that are nearly a.n.a.lagous to fermentation, and that such diseases are therefore traceable ultimately to the existence of living germs.

This view of the case brought Pasteur to a large and general investigation of bacteria. The bacterium may be defined as a microscopic vegetable organism; or it may be called an _animal_ organism; for in the deep-down life of germs there is not much difference between vegetable and animal--perhaps no difference at all.

The bacterium is generally a jointed rod-like filament of living matter, and its native world seems to be any putrefying organic substance.

Bacteria are the smallest of microscopic organisms. They are widely diffused in the natural world, existing independently and also in a parasitical way, in connection with larger forms of organic life. They multiply with the greatest rapidity. On the whole, the bacterium fulfills its vital offices in two ways, or with two results; first, _fermentation_, and secondly, _disease_.

To this field of inquiry Pasteur devoted himself with the greatest a.s.siduity. He began to investigate the diseased tissue of animals, and was rewarded with the discovery of the germs from which the disease had come. It was found that the bacteria of one disease are different from those of another disease, or in a word that the microscopic organisms which produce morbid conditions in animals are differentiated into genera and species and varieties, in the same manner as are the animals, birds and fishes, of the world. A new realm of life invisible save by the aid of the microscope, began to be explored, and practical results began to follow.

Pasteur at length announced his ability to _produce_ infectious diseases by inoculation; and of this his proofs and demonstrations, were complete. In the next place he announced his ability to _counteract_ the ravages, of certain cla.s.ses of diseases (those called zymotic) by inoculating the animal suffering therefrom with what he called an "attenuated" or "domesticated" virus of the given disease.

The matter first came to a practical issue by the inoculation of well animals with the attenuated virus. The animals so treated became _immune_; that is, exempt from the infection of the given disease.

Pasteur gave public demonstrations in the fields near Paris, using the disease called splenic fever, and sheep as the subjects of his experimentation. The whole civilized world was astonished with the results. The tests were conducted in such a way as to preclude the possibility of error. It was shown, in a word, that by the simple process of inoculating well animals with the modified poison the infectious disease might be avoided.

It were long to tell the story of the experimentation and discovery that now followed. The last quarter of the century has been fruitful in the greatest results. The bacilli of one disease after another have been discovered, and the means have been invented of defending the larger animal life from the ravages of microscopic organisms.

But what is an "attenuated" virus? Pasteur and other scientists have shown that by the inoculation of suitable material, such as a piece of flesh, with the poison of a given disease, the bacteria on which that disease depends rapidly multiply and diffuse themselves through the substance. If poison be taken from the _first_ body of infected material and carried to _another_, that other becomes infected; and from that the third; from the third the fourth, and so on to the tenth generation.

It was noticed, however, that with each transference of the virus to a new organic body the bacilli were modified somewhat in form and activity. They became, so to speak, less savage. The bacterium which at the beginning had been for its savagery a wolf, became in the second body a cur; then a hound; then a spaniel; and then a diminutive lapdog! The bacteria were thus said to be "domesticated;"

for the process was similar to the domestication of wild animals into tame. The virus was said to be "attenuated;" that is, made thin or fine; that is, its poisonous and death-dealing quality, was so reduced as to make it comparatively innocuous.

If after the process of attenuation was complete--if after the bacteria were once thoroughly domesticated and the poison produced by them be then introduced into a well subject, that subject would indeed become diseased, but so mildly diseased as scarcely to be diseased at all. In such a case the result was of a kind to be called in popular language a mere "touch" of the disease. In such case the severe ravages of the malady would be prevented; but the subject would be rendered incapable of taking the disease a second time.

On this line of fact and theory Pasteur successfully pressed his work.