THE first patent that was ever granted on a device for permanently recording the human voice and other sounds, and for reproducing the same audibly at any future time, was United States Patent No. 200,251, issued to Thomas A. Edison on February 19, 1878, the application having been filed December 24, 1877. It is worthy of note that no references whatever were cited against the application while under examination in the Patent Office. This invention therefore, marked the very beginning of an entirely new art, which, with the new industries attendant upon its development, has since grown to occupy a position of worldwide reputation.

That the invention was of a truly fundamental character is also evident from the fact that although all "talking-machines" of to-day differ very widely in refinement from the first crude but successful phonograph of Edison, their performance is absolutely dependent upon the employment of the principles stated by him in his Patent No. 200,251. Quoting from the specification attached to this patent, we find that Edison said:

"The invention consists in arranging a plate, diaphragm or other flexible body capable of being vibrated by the human voice or other sounds, in conjunction with a material capable of registering the movements of such vibrating body by embossing or indenting or altering such material, in such a manner that such register marks will be sufficient to cause a second vibrating plate or body to be set in motion by them, and thus reproduce the motions of the first vibrating body."

It will be at once obvious that these words describe perfectly the basic principle of every modern phonograph or other talking-machine, irrespective of its manufacture or trade name.

Edison's first model of the phonograph is shown in the following illustration.

It consisted of a metallic cylinder having a helical indenting groove cut upon it from end to end. This cylinder was mounted on a shaft supported on two standards. This shaft at one end was fitted with a handle, by means of which the cylinder was rotated. There were two diaphragms, one on each side of the cylinder, one being for recording and the other for reproducing speech or other sounds. Each diaphragm had attached to it a needle. By means of the needle attached to the recording diaphragm, indentations were made in a sheet of tin-foil stretched over the peripheral surface of the cylinder when the diaphragm was vibrated by reason of speech or other sounds. The needle on the other diaphragm subsequently followed these indentations, thus reproducing the original sounds.

Crude as this first model appears in comparison with machines of later development and refinement, it embodied their fundamental essentials, and was in fact a complete, practical phonograph from the first moment of its operation.

The next step toward the evolution of the improved phonograph of to-day was another form of tin-foil machine, as seen in the illustration.

It will be noted that this was merely an elaborated form of the first model, and embodied several mechanical modifications, among which was the employment of only one diaphragm for recording and reproducing. Such was the general type of phonograph used for exhibition purposes in America and other countries in the three or four years immediately succeeding the date of this invention.

In operating the machine the recording diaphragm was advanced nearly to the cylinder, so that as the diaphragm was vibrated by the voice the needle would prick or indent a wave-like record in the tin-foil that was on the cylinder. The cylinder was constantly turned during the recording, and in turning, was simultaneously moved forward. Thus the record would be formed on the tin-foil in a continuous spiral line. To reproduce this record it was only necessary to again start at the beginning and cause the needle to retrace its path in the spiral line. The needle, in passing rapidly in contact with the recorded waves, was vibrated up and down, causing corresponding vibrations of the diaphragm. In this way sound-waves similar to those caused by the original sounds would be set up in the air, thus reproducing the original speech.

The modern phonograph operates in a precisely similar way, the only difference being in details of refinement. Instead of tin-foil, a wax cylinder is employed, the record being cut thereon by a cutting-tool attached to a diaphragm, while the reproduction is effected by means of a blunt stylus similarly attached.

The cutting-tool and stylus are devices made of sapphire, a gem next in hardness to a diamond, and they have to be cut and formed to an exact nicety by means of diamond dust, most of the work being performed under high-powered microscopes. The minute proportions of these devices will be apparent by a glance at the accompanying illustrations, in which the object on the left represents a common pin, and the objects on the right the cutting-tool and reproducing stylus, all actual sizes.

In the next illustration (Fig. 4) there is shown in the upper sketch, greatly magnified, the cutting or recording tool in the act of forming the record, being vibrated rapidly by the diaphragm; and in the lower sketch, similarly enlarged, a representation of the stylus travelling over the record thus made, in the act of effecting a reproduction.

From the late summer of 1878 and to the fall of 1887 Edison was intensely busy on the electric light, electric railway, and other problems, and virtually gave no attention to the phonograph. Hence, just prior to the latter-named period the instrument was still in its tin-foil age; but he then began to devote serious attention to the development of an improved type that should be of greater commercial importance. The practical results are too well known to call for further comment. That his efforts were not limited in extent may be inferred from the fact that since the fall of 1887 to the present writing he has been granted in the United States one hundred and four patents relating to the phonograph and its accessories.

Interesting as the numerous inventions are, it would be a work of supererogation to digest all these patents in the present pages, as they represent not only the inception but also the gradual development and growth of the wax-record type of phonograph from its infancy to the present perfected machine and records now so widely known all over the world. From among these many inventions, however, we will select two or three as examples of ingenuity and importance in their bearing upon present perfection of results.

One of the difficulties of reproduction for many years was the trouble experienced in keeping the stylus in perfect engagement with the wave-like record, so that every minute vibration would be reproduced. It should be remembered that the deepest cut of the recording tool is only about one-third the thickness of tissue-paper. Hence, it will be quite apparent that the slightest inequality in the surface of the wax would be sufficient to cause false vibration, and thus give rise to distorted effects in such music or other sounds as were being reproduced. To remedy this, Edison added an attachment which is called a "floating weight," and is shown at A in the illustration above.

The function of the floating weight is to automatically keep the stylus in close engagement with the record, thus insuring accuracy of reproduction. The weight presses the stylus to its work, but because of its mass it cannot respond to the extremely rapid vibrations of the stylus. They are therefore communicated to the diaphragm.

Some of Edison's most remarkable inventions are revealed in a number of interesting patents relating to the duplication of phonograph records. It would be obviously impossible, from a commercial standpoint, to obtain a musical record from a high-class artist and sell such an original to the public, as its cost might be from one hundred to several thousand dollars. Consequently, it is necessary to provide some way by which duplicates may be made cheaply enough to permit their purchase by the public at a reasonable price.

The making of a perfect original musical or other record is a matter of no small difficulty, as it requires special technical knowledge and skill gathered from many years of actual experience; but in the exact copying, or duplication, of such a record, with its many millions of microscopic waves and sub-waves, the difficulties are enormously increased. The duplicates must be microscopically identical with the original, they must be free from false vibrations or other defects, although both original and duplicates are of such easily defacable material as wax; and the process must be cheap and commercial not a scientific laboratory possibility.

For making duplicates it was obviously necessary to first secure a mold carrying the record in negative or reversed form. From this could be molded, or cast, positive copies which would be identical with the original. While the art of electroplating would naturally suggest itself as the means of making such a mold, an apparently insurmountable obstacle appeared on the very threshold. Wax, being a non-conductor, cannot be electroplated unless a conducting surface be first applied. The coatings ordinarily used in electro-deposition were entirely out of the question on account of coarseness, the deepest waves of the record being less than one-thousandth of an inch in depth, and many of them probably ten to one hundred times as shallow. Edison finally decided to apply a preliminary metallic coating of infinitesimal thinness, and accomplished this object by a remarkable process known as the vacuous deposit. With this he applied to the original record a film of gold probably no thicker than one three-hundred-thousandth of an inch, or several hundred times less than the depth of an average wave. Three hundred such layers placed one on top of the other would make a sheet no thicker than tissue-paper.

The process consists in placing in a vacuum two leaves, or electrodes, of gold, and between them the original record. A constant discharge of electricity of high tension between the electrodes is effected by means of an induction-coil. The metal is vaporized by this discharge, and is carried by it directly toward and deposited upon the original record, thus forming the minute film of gold above mentioned. The record is constantly rotated until its entire surface is coated. A sectional diagram of the apparatus (Fig. 6.) will aid to a clearer understanding of this ingenious process.

After the gold film is formed in the manner described above, a heavy backing of baser metal is electroplated upon it, thus forming a substantial mold, from which the original record is extracted by breakage or shrinkage.

Duplicate records in any quantity may now be made from this mold by surrounding it with a cold-water jacket and dipping it in a molten wax-like material. This congeals on the record surface just as melted butter would collect on a cold knife, and when the mold is removed the surplus wax falls out, leaving a heavy deposit of the material which forms the duplicate record. Numerous ingenious inventions have been made by Edison providing for a variety of rapid and economical methods of duplication, including methods of shrinking a newly made copy to facilitate its quick removal from the mold; methods of reaming, of forming ribs on the interior, and for many other important and essential details, which limits of space will not permit of elaboration. Those mentioned above are but fair examples of the persistent and effective work he has done to bring the phonograph to its present state of perfection.

In perusing Chapter X of the foregoing narrative, the reader undoubtedly noted Edison's clear apprehension of the practical uses of the phonograph, as evidenced by his prophetic utterances in the article written by him for the North American Review in June, 1878. In view of the crudity of the instrument at that time, it must be acknowledged that Edison's foresight, as vindicated by later events was most remarkable. No less remarkable was his intensely practical grasp of mechanical possibilities of future types of the machine, for we find in one of his early English patents (No. 1644 of 1878) the disk form of phonograph which, some ten to fifteen years later, was supposed to be a new development in the art. This disk form was also covered by Edison's application for a United States patent, filed in 1879. This application met with some merely minor technical objections in the Patent Office, and seems to have passed into the "abandoned" class for want of prosecution, probably because of being overlooked in the tremendous pressure arising from his development of his electric-lighting system.

IX. THE INCANDESCENT LAMP

ALTHOUGH Edison's contributions to human comfort and progress are extensive in number and extraordinarily vast and comprehensive in scope and variety, the universal verdict of the world points to his incandescent lamp and system of distribution of electrical current as the central and crowning achievements of his life up to this time. This view would seem entirely justifiable when we consider the wonderful changes in the conditions of modern life that have been brought about by the wide-spread employment of these inventions, and the gigantic industries that have grown up and been nourished by their world-wide application. That he was in this instance a true pioneer and creator is evident as we consider the subject, for the United States Patent No. 223,898, issued to Edison on January 27, 1880, for an incandescent lamp, was of such fundamental character that it opened up an entirely new and tremendously important art—the art of incandescent electric lighting. This statement cannot be successfully controverted, for it has been abundantly verified after many years of costly litigation. If further proof were desired, it is only necessary to point to the fact that, after thirty years of most strenuous and practical application in the art by the keenest intellects of the world, every incandescent lamp that has ever since been made, including those of modern days, is still dependent upon the employment of the essentials disclosed in the above-named patent—namely, a filament of high resistance enclosed in a sealed glass globe exhausted of air, with conducting wires passing through the glass.

An incandescent lamp is such a simple-appearing article—merely a filament sealed into a glass globe—that its intrinsic relation to the art of electric lighting is far from being apparent at sight. To the lay mind it would seem that this must have been THE obvious device to make in order to obtain electric light by incandescence of carbon or other material. But the reader has already learned from the preceding narrative that prior to its invention by Edison such a device was NOT obvious, even to the most highly trained experts of the world at that period; indeed, it was so far from being obvious that, for some time after he had completed practical lamps and was actually lighting them up twenty-four hours a day, such a device and such a result were declared by these same experts to be an utter impossibility. For a short while the world outside of Menlo Park held Edison's claims in derision. His lamp was pronounced a fake, a myth, possibly a momentary success magnified to the dignity of a permanent device by an overenthusiastic inventor.

Such criticism, however, did not disturb Edison. He KNEW that he had reached the goal. Long ago, by a close process of reasoning, he had clearly seen that the only road to it was through the path he had travelled, and which was now embodied in the philosophy of his incandescent lamp—namely, a filament, or carbon, of high resistance and small radiating surface, sealed into a glass globe exhausted of air to a high degree of vacuum. In originally committing himself to this line of investigation he was well aware that he was going in a direction diametrically opposite to that followed by previous investigators. Their efforts had been confined to low-resistance burners of large radiating surface for their lamps, but he realized the utter futility of such devices. The tremendous problems of heat and the prohibitive quantities of copper that would be required for conductors for such lamps would be absolutely out of the question in commercial practice.

He was convinced from the first that the true solution of the problem lay in a lamp which should have as its illuminating body a strip of material which would offer such a resistance to the flow of electric current that it could be raised to a high temperature—incandescence—and be of such small cross-section that it would radiate but little heat. At the same time such a lamp must require a relatively small amount of current, in order that comparatively small conductors could be used, and its burner must be capable of withstanding the necessarily high temperatures without disintegration.

It is interesting to note that these conceptions were in Edison's mind at an early period of his investigations, when the best expert opinion was that the subdivision of the electric current was an ignis fatuus. Hence we quote the following notes he made, November 15, 1878, in one of the laboratory note-books:

"A given straight wire having 1 ohm resistance and certain length is brought to a given degree of temperature by given battery. If the same wire be coiled in such a manner that but one-quarter of its surface radiates, its temperature will be increased four times with the same battery, or, one-quarter of this battery will bring it to the temperature of straight wire. Or the same given battery will bring a wire whose total resistance is 4 ohms to the same temperature as straight wire.

"This was actually determined by trial.

"The amount of heat lost by a body is in proportion to the radiating surface of that body. If one square inch of platina be heated to 100 degrees it will fall to, say, zero in one second, whereas, if it was at 200 degrees it would require two seconds.

"Hence, in the case of incandescent conductors, if the radiating surface be twelve inches and the temperature on each inch be 100, or 1200 for all, if it is so coiled or arranged that there is but one-quarter, or three inches, of radiating surface, then the temperature on each inch will be 400. If reduced to three-quarters of an inch it will have on that three-quarters of an inch 1600 degrees Fahr., notwithstanding the original total amount was but 1200, because the radiation has been reduced to three-quarters, or 75 units; hence, the effect of the lessening of the radiation is to raise the temperature of each remaining inch not radiating to 125 degrees. If the radiating surface should be reduced to three-thirty-seconds of an inch, the temperature would reach 6400 degrees Fahr. To carry out this law to the best advantage in regard to platina, etc., then with a given length of wire to quadruple the heat we must lessen the radiating surface to one-quarter, and to do this in a spiral, three-quarters must be within the spiral and one-quarter outside for radiating; hence, a square wire or other means, such as a spiral within a spiral, must be used. These results account for the enormous temperature of the Electric Arc with one horse-power; as, for instance, if one horse-power will heat twelve inches of wire to 1000 degrees Fahr., and this is concentrated to have one-quarter of the radiating surface, it would reach a temperature of 4000 degrees or sufficient to melt it; but, supposing it infusible, the further concentration to one-eighth its surface, it would reach a temperature of 16,000 degrees, and to one-thirty-second its surface, which would be about the radiating surface of the Electric Arc, it would reach 64,000 degrees Fahr. Of course, when Light is radiated in great quantities not quite these temperatures would be reached.

"Another curious law is this: It will require a greater initial battery to bring an iron wire of the same size and resistance to a given temperature than it will a platina wire in proportion to their specific heats, and in the case of Carbon, a piece of Carbon three inches long and one-eighth diameter, with a resistance of 1 ohm, will require a greater battery power to bring it to a given temperature than a cylinder of thin platina foil of the same length, diameter, and resistance, because the specific heat of Carbon is many times greater; besides, if I am not mistaken, the radiation of a roughened body for heat is greater than a polished one like platina."

Proceeding logically upon these lines of thought and following them out through many ramifications, we have seen how he at length made a filament of carbon of high resistance and small radiating surface, and through a concurrent investigation of the phenomena of high vacua and occluded gases was able to produce a true incandescent lamp. Not only was it a lamp as a mere article—a device to give light—but it was also an integral part of his great and complete system of lighting, to every part of which it bore a fixed and definite ratio, and in relation to which it was the keystone that held the structure firmly in place.

The work of Edison on incandescent lamps did not stop at this fundamental invention, but extended through more than eighteen years of a most intense portion of his busy life. During that period he was granted one hundred and forty-nine other patents on the lamp and its manufacture. Although very many of these inventions were of the utmost importance and value, we cannot attempt to offer a detailed exposition of them in this necessarily brief article, but must refer the reader, if interested, to the patents themselves, a full list being given at the end of this Appendix. The outline sketch will indicate the principal patents covering the basic features of the lamp.

The litigation on the Edison lamp patents was one of the most determined and stubbornly fought contests in the history of modern jurisprudence. Vast interests were at stake. All of the technical, expert, and professional skill and knowledge that money could procure or experience devise were availed of in the bitter fights that raged in the courts for many years. And although the Edison interests had spent from first to last nearly $2,000,000, and had only about three years left in the life of the fundamental patent, Edison was thoroughly sustained as to priority by the decisions in the various suits. We shall offer a few brief extracts from some of these decisions.

In a suit against the United States Electric Lighting Company, United States Circuit Court for the Southern District of New York, July 14, 1891, Judge Wallace said, in his opinion: "The futility of hoping to maintain a burner in vacuo with any permanency had discouraged prior inventors, and Mr. Edison is entitled to the credit of obviating the mechanical difficulties which disheartened them.... He was the first to make a carbon of materials, and by a process which was especially designed to impart high specific resistance to it; the first to make a carbon in the special form for the special purpose of imparting to it high total resistance; and the first to combine such a burner with the necessary adjuncts of lamp construction to prevent its disintegration and give it sufficiently long life. By doing these things he made a lamp which was practically operative and successful, the embryo of the best lamps now in commercial use, and but for which the subdivision of the electric light by incandescence would still be nothing but the ignis fatuus which it was proclaimed to be in 1879 by some of the reamed experts who are now witnesses to belittle his achievement and show that it did not rise to the dignity of an invention.... It is impossible to resist the conclusion that the invention of the slender thread of carbon as a substitute for the burners previously employed opened the path to the practical subdivision of the electric light."

An appeal was taken in the above suit to the United States Circuit Court of Appeals, and on October 4, 1892, the decree of the lower court was affirmed. The judges (Lacombe and Shipman), in a long opinion reviewed the facts and the art, and said, inter alia: "Edison's invention was practically made when he ascertained the theretofore unknown fact that carbon would stand high temperature, even when very attenuated, if operated in a high vacuum, without the phenomenon of disintegration. This fact he utilized by the means which he has described, a lamp having a filamentary carbon burner in a nearly perfect vacuum."

In a suit against the Boston Incandescent Lamp Company et al., in the United States Circuit Court for the District of Massachusetts, decided in favor of Edison on June 11, 1894, Judge Colt, in his opinion, said, among other things: "Edison made an important invention; he produced the first practical incandescent electric lamp; the patent is a pioneer in the sense of the patent law; it may be said that his invention created the art of incandescent electric lighting."

Opinions of other courts, similar in tenor to the foregoing, might be cited, but it would be merely in the nature of reiteration. The above are sufficient to illustrate the direct clearness of judicial decision on Edison's position as the founder of the art of electric lighting by incandescence.