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 God. It remained for the evangelist to declare that God 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 principal 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 Röntgen rays has been made. The results which seem likely to flow from this marvelous revelation surpass 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 Röntgen, of Würzburg, made the discovery which seems likely to contribute so much to our knowledge of the mysterious processes of nature. On that day Dr. Röntgen 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 glass 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 passed 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 constituting 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 Röntgen 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. Röntgen himself called the phenomena the X, or unknown, rays.
In the experimentation referred to, Röntgen had covered the glass 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 Röntgen 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 glass, 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 glass 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 Röntgen soon announced his discovery to the Physico-Medical Society of Würzburg. 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 Röntgen'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 Röntgen 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 Röntgen 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. Röntgen 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 pass 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 Röntgen 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 pass 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. Glass 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 constitution of the physical universe; and that one supreme force is gravitation!