It were vain to speculate upon the future of electric lighting. The question of artificial illumination has had much to do with the progress of the human race, particularly when aggregated into cities. Doubtless the old systems of lighting are destined in time to give place altogether to the splendors of the electric glow. The general effect of the change upon society must be as marked as it is salutary. Darkness, the enemy of good government and morality in great cities, will, in great measure, be dispelled by the beneficent agent, over which the genius of Davy, Gramme, Brush, Edison, and a host of other explorers in the new continents of science has so completely triumphed. The ease, happiness, comfort, and welfare of mankind must be vastly multiplied, and the future must be reminded, in the glow that dispels the night, of that splendid fact that the progress of civilization depends, in a large measure, upon a knowledge of Nature's laws, and the diffusion of that knowledge among the people.

THE TELEPHONE.

Perhaps no other great invention of man has been within so short a period so widely distributed as the telephone. The use of the instrument is already co-extensive with civilization. The cost at which the instruments are furnished is still so considerable that the poor of the world are not able to avail themselves of the invention; but in the so-called upper circles of society the use of the telephone is virtually universal. It has made its way from the city to the town, from the town to the village, from the village to the hamlet, and even to the country-side where the millions dwell.

The telephone came by a speedy revelation. It was born of that intense scientific activity which is the peculiarity of our age. The antecedent knowledge out of which it sprang had existed in various forms for a long time. The laws of acoustics were among the first to be investigated after a true physical science began to be taught. The phenomena of sound are so universal and experimentation in sound production so easy, that the governing laws were readily discovered.

Acoustics, we think, foreran somewhat the science of heat, as the science of heat preceded that of light. Electricity came last. The telephone is an instrument belonging not wholly, not chiefly, but only in part, to acoustics. It owes its existence to magnetic induction and electrical transmission as much as to the mere action of sound. One foot of the instrument, so to speak, is acoustics, and the other foot electricity. The telephone philosophically considered is an instrument for the conversion of a sound-wave into electrical motion, and its reconversion into sound at a distance. The sound is, as it were, committed to the electrical current and is thus sent to the end of the journey, and there discharged with its message. The possibility of this result lies first of all in the fact of electrical transmission by wire, and in the second place to the mounting of a sound-rider on the electrical saddle for an instantaneous journey with important despatches!

New results in scientific progress generally seem marvelous. The unfamiliar and unexpected thing is always a marvel; but scientifically considered, the telephone does not seem so surprising as at first view. The atmosphere is a conductor of sound. It is the natural agent of transmission, and so far as the natural man is concerned, it is his only agent for the transmission of oral utterance. If the unlearned man have his attention called to the surprising fact of hearing his fellow-man call out to him across a field or from far off on the prairie, he does not think it marvelous, but only natural. Yet how strange it is that one human being can speak to another through the intervening space!

It is strange that one should see another at a distance; but seeing and hearing at distances are natural functions of living creatures. The sunlight is for one sense and the sound-wave is for the other. The sound-wave travels on the atmosphere, and preserves its integrity. A given sound is produced, and the same sound is heard by some ear at a distance. All the people of the world are telephoning to one another; for oral speech leaping from the vocal organs of one human being to the ear of another is always telephonic. It is only when this phenomenon of speech at a distance is taken from the soft wings of the air, confined to a wire, and made to fly along the slender thread and deliver itself afar in a manner to which the world has hitherto been a stranger that the thing done and the apparatus by which it is done seem miraculous. Indeed it is a miracle; for miraculum signifies wonderful.

The history of the invention of the telephone is easily apprehended. The scientific principles on which it depends may be understood without difficulty. There is, however, about the instrument and its action something that is well nigh unbelievable. It is essentially a thing contrary to universal experience, if not positively inconceivable, that the slight phenomenon of the human voice should be, so to speak, picked up by a physical contrivance, carried a thousand miles through a thread of wire not a quarter of an inch in diameter, and delivered in its integrity to the sense of another waiting to receive it! At all events, the history of the telephone, belonging so distinctly to our own age, will stand as a reminder to after times of the great stride which the human race made in inventive skill and scientific progress in the last quarter of the nineteenth century.

The telephone, like many similar instruments, was the work of several ingenious minds directed at nearly the same time to the same problem. The solution, however, must be accredited first of all to Elisha P. Gray, of Chicago, and Alexander Graham Bell, of the Massachusetts Institute of Technology. It should be mentioned, however, that Amos E. Dolbear, of Tufts College, Massachusetts, and Thomas A. Edison, of Menlo Park, New Jersey, likewise succeeded in solving the difficulty in the way of telephonic communication, and in answering practically several of the minor questions that hindered at first the complete success of the invention. The telephone is an instrument for the reproduction of sounds, particularly the sounds of the human voice, by the agency of electrical conduction at long distances from the origin of the vocal disturbance. Or it may be defined as an instrument for the transmission of the sounds referred to by the agencies described. Indeed it were hard to say whether in a telephonic message we receive a reproduced sound or a transmitted sound. On the whole, it is more proper to speak of a reproduction of the original sound by transmission of the waves in which that sound is first written.

It is now well known that the phenomenon called sound consists of a wave agitation communicated through the particles of some medium to the organ of hearing. Every particular sound has its own physical equivalent in the system of waves in which it is written. The only thing, therefore, that is necessary in order to carry a sound in its integrity to any distance, is to transmit its physical equivalent, and to redeliver that equivalent to some organ of hearing capable of receiving it.

Upon these principles the telephone was produced—created. Every sound which falls by impact upon the sheet-iron disk of the instrument communicates thereto a sort of tremor. This tremor causes the disk to approach and recede from the magnetic pole placed just behind the diaphragm. A current of electricity is thus induced, pulsates along the wire to the other end, and is delivered to the metallic disk of the second instrument, many miles away, just as it was produced in the first. The ear of the hearer receives from the second instrument the exact physical equivalent of the sound, or sounds, which were delivered against the disk of the first instrument, and thus the utterance is received at a distance just as it was given forth.

As already said, the invention of the telephone stands chiefly to the credit of Professors Gray and Bell. It should be recorded that as early as 1837, the philosopher Page succeeded, by means of electro-magnetism, in transmitting musical tones to a distance. It was not, however, until 1877 that Professer Bell, in a public lecture given at Salem, Mass., astonished his audience, and the whole country as well, by receiving and transmitting vocal messages from Boston, twenty miles away. Incredulity had no more a place as it respected the feasibility of talking to persons at a distance. The experiments of Gray at Chicago, a few days later in the same month, were equally successful. Messages were distinctly delivered between that city and Milwaukee, a distance of eighty-five miles, nor could it be longer doubted that a new era in the means of communication had come.

The Bell telephone, with its many modifications and improvements, has come into rapid use. Within reasonable limits of distance, the new method of transmitting intelligence by direct vocal utterance, has taken the place of all slower and less convenient means of intercommunication. The appearance of the simple instrument has been one of the many harbingers of the oncoming better time, when the interchange of thought and sentiment between man and man, community and community, nation and nation, and race and race shall be the preliminary of universal peace in the world and of the good-fellowship of mankind.

Every such fact as the invention of the telephone, produces a complex and almost indescribable result in human society. This result has in it, in the first place, a change in the manners and method of the individual There is also a change in his sentiments. He whose work in life, whatever it may be, is accomplished in touch with the telephone will realize that he is in touch with the whole world. This intimacy reaches, first, his neighbors and friends. He seems to live henceforth in their presence, and in communication with them.

The isolation of the individual life is virtually obliterated by such an agency. Solitude disappears before it; for he whose ear is within hearing of his instrument, knows not at what moment any one of many thousands of people may speak to him. He knows not at what moment intelligence of an ever-varying kind may be spoken to him from his own community or out of the depths of distance. The mind is thus affiliated with an enlarged and ever-present society. These considerations do not relate to mere matters of convenience and quickness and advantage and safety, but to the larger question of the aggregate effect upon the individual.

The effect on the community is of like kind. The community is no longer so segregated as it was before. The community is in touch with other communities of like character. The conflagration in one town is felt in the neighboring towns, if it is not seen. The epidemic of the one is the epidemic of many. The sensation of the one community diffuses itself instantly into several. The effect is in the intellectual life like that of a wave produced on the lake by the casting in of a stone. The wave widens and recedes. It may be obstructed or unobstructed in its progress. If obstructed, the obstructions may be removed. Then the motion of the wave will become free and regular. So also on the tide of public thought. The telephone is an agency for removing mental obstructions, and for the regular diffusion of a common thought.

All this, however, is attended with draw-backs. One of these is the breaking in on the privacy and seclusion of the individual life. Individuality suffers under scientific progress. Great thinking is accomplished best in solitude. Emerson has forcibly pointed out the advantages which arise in the intellectual life from its isolation and seclusion—from its free and uninterrupted communion with itself.

The convenience—the physical convenience—of life is vastly augmented by such a contrivance as the telephone. Time is saved and trouble obviated. But at the same time the necessity for bodily exercise is reduced, and the overgrowth of brain at the expense of body encouraged. The fact is that the invention of the telephone and its general use, while it has added very greatly to the comfort of life, while it has promoted ease and diffused a social sense that needed stimulation and development, has at the same time brought in conditions that are not wholly favorable to human welfare. More largely still, the truth is that the telephone, like every other symbol and agency of progress, has brought enlarged responsibilities.

No man, no community, no people or nation can gain an increase of power without accepting the accompanying increase of responsibility. The moral nature of man is thus involved. Every forward stride of scientific invention places upon the life of man, including his bodily activity, his mental moods and his spiritual and moral powers, an added stress of duty, of energy, and of rectitude in conduct from which he may not shrink if he would be the gainer rather than the loser. Each discovery and each improved method of employing the beneficent forces of the natural world, brings with it a strain upon the moral nature of man which, if he stand it, well; but if he stand it not, then it shall go ill with him.

THE MACHINE THAT "TALKS BACK."

The invention for making nature give an intelligent response may well be regarded with wondering interest. The odd, we might say humorous, feature of the invention is that nature, being as it were cornered and compelled to respond, will answer nothing except to repeat what is said in her ear! The phonograph may be defined as a mechanical parrot. Unlike the living bird, however, it never makes answers malapropos. It never deviates from the original text. The distrust which has been justly cherished against the talking bird on account of his originality can never be reasonably directed against the phonograph!

The possibility of writing sound has been recognized for a century past. Since the discovery of the vibratory character of sound, the physicist has seen the feasibility of recording the vibration. Nature herself has given many hints along this line of experimentation. Long ago it was seen that the writing sand sprinkled on the sounding board of the piano would under the influence of a chord struck from the keys arrange itself in geometrical figures. It was also seen that a discord sounded from the key-board would break the figures into chaos and confusion. Were not these phenomena sufficient to suggest that sound might be written in intelligible characters?

The mind, however, moves slowly from the old to the new. The former concept of physical facts and the laws which govern them is not readily given up. A great discovery in physical science seems to disturb the foundations of nature. It does not really do so; the disturbance is not in nature, but in the mind. No endeavor of man, no advance of his from some old bivouac to a new camping-ground, affects in the least the order of the world. The change, we repeat, is in the man, and in the race to which he belongs.

Long and tedious has been the process of getting thought into a recorded form. The first method of expressing thought was oral. Long before any other method of holding ideas and delivering them to others was devised or imagined, speech came. Speech is oral. It is made of sound. Oral utterance is no doubt as old as the race itself. It began with the first coming of our kind into this sphere. Indeed we now know that the rudiments of speech exist in the faculties of the lower animals. The studies of Professor Garner have shown conclusively that the humble simian folk of the African forest have a speech or language. Of this the professor himself has become a student, and he claims to have learned at least sixty words of the vocabulary!

Strange it is to note the course which linguistic development has taken. At the first, there was a spoken language only. The next stage was to get this spoken language recorded, not in audible, but in visible symbols. Why should it have been so easy and apparently natural for the old races to invent a visible form of speech-writing rather than an audible form? Why should the ancients have fallen back on the eye rather than the ear as the sense to be instructed? Why should sight-writing have been invented thousands of years ago, and sound-writing postponed until the present day?

In any event, such has been the history of recorded language. The early races began as the mother begins with her children; that is, with oral speech. But at a certain stage this method was abandoned, and teachers came with pictorial symbols of words. They invented visible characters to signify words, syllables, sounds. Thus came alphabetical writing, syllabic writing, verbal writing, into the world. Ever afterward the children of men learned speech first from their parents, by oral utterance; but afterward by means of the pictorial signs in which human language was recorded.

This method became habitual. The eye was made to be the servant of the intellect in learning nearly all that was to be gained from the wisdom of the past. It was by the tedious way of crooked marks signifying words that ideas were henceforth gleaned out of human lore by all who would learn aught from the recorded wisdom of mankind. And yet there never was anything essentially absurd or insurmountable in the invention of a method of recording speech in audible instead of visible symbols.

The phonograph came swiftly after the telephone. The new instrument is in a sense the complement of its predecessor. Both inventions are based upon the same principle in science. The discovery that every sound has its physical equivalent in a wave or agitation which affects the particles of matter composing the material through which the sound is transmitted led almost inevitably to the other discovery of catching and retaining that physical equivalent or wave in the surface of some body, and to the reproduction of the original sound therefrom.

Such is the fundamental principle of the interesting but, thus far, little useful instrument known as the phonograph. The same was invented by Thomas A. Edison, of Menlo Park, in the year 1877. The instrument differs considerably in structure and purpose from the Vibrograph and Phonautograph which preceded it. The latter two instruments were made simply to write sound vibrations; the former, to reproduce audibly the sounds themselves.

The phonograph consists of three principal parts,—the sender or funnel-shaped tube, with its open mouth-piece standing toward the operator; the diaphragm and stylus connected therewith, which receives the sound spoken into the tube; and thirdly, the revolving cylinder, with its sheet-coating of tin-foil laid over the surface of a spiral groove to receive the indentations of the point of the stylus. The mode of operation is very simple. The cylinder is revolved; and the point of the stylus, when there is no sound agitation in the funnel or mouth-piece, makes a smooth, continuous depression in the tin-foil over the spiral groove. But when any sound is thrown into the mouth-piece the iron disk or diaphragm is agitated; this agitation is carried through the stylus and written in irregular marks, dots, and peculiar figures in the tin-foil over the groove.

When the utterance which is to be reproduced has been completed, the instrument is stopped, the stylus thrown back from the groove, and the cylinder revolved backward to the place of starting. The stylus is then returned to its place in the groove, and the cylinder is revolved forward at the same rate of rapidity as before. As the point of the stylus plays up and down in the indentations and through the figures in the tin-foil, produced by its own previous agitation, a quiver exactly equivalent to that which was produced by the utterance in the mouth-piece is thrown into the air. This agitation is of course the exact physical equivalent of the original sound, or, more properly, is the sound itself. Thus it is that the phonograph is made to talk, to sing, to cry; to utter, in short, any sound sufficiently powerful to produce a perceptible tremor in the mouth-piece and diaphragm of the instrument.

Much progress has been made toward the utilization of the phonograph as a practical addition to the civilizing apparatus of our time. It may be said, indeed, that all the difficulties in the way of such a result have been removed. Mr. Edison has carried forward his work to such a degree of perfection that the instrument may be practically employed in correspondence and literary composition. The problem has been to stereotype, so to speak, the tin-foil record of what has been uttered in the mouth-piece, and thus to preserve in a permanent form the potency of vanished sounds. Nor does it require a great stretch of the imagination to see in the invention of the phonograph one of the greatest achievements of the age—a discovery, indeed, which may possibly revolutionize the whole method of learning.

It would seem clear that nature has intended the ear, rather than the eye, to be the organ of education. It is manifestly against the fitness of things that the eyes of all mankind should be strained, weakened, permanently injured in childhood, with the unnatural tasks which are imposed upon the delicate organ. It would seem to be more in accordance with the nature and capacities of man, and the general character of the external world, to reserve the eye for the discernment and appreciation of beauty, and to impose upon the ear the tedious and hard tasks of education.

The phonograph makes it possible to read by the ear instead of by the eye, and it is not beyond the range of probability that the book of the future, near or remote, will be written in phonographic plates and made to reveal its story directly to the waiting ear, rather than through the secondary medium of print to the enfeebled and tired eye of the reader.

We hardly venture on prophecy; but we think that he who returns to this scene of human activity at the close of the twentieth century will find that sound has been substituted for sight in nearly everything that relates to recorded information, to learning, and to educational work. By that means the organ of hearing will be restored to its rightful office. Enlightenment and instruction of all kinds will be given by means of phonographic books. The sound-wave will, in a word, be substituted for the light-wave as the vehicle of all our best information and intercourse. The ear will have habitually taken the place of the eye in the principal offices of interest and information.

The unnatural method of the book—the visible book instead of the audible book—will then be done away. Nature, who instructs the child by sound, will continue to teach the man in the same manner. All mothers, from the mother bird to the mother woman, begin the teaching of their offspring by sound, by utterance. The mother bird continues in this manner; but the mother woman is presently supplanted by a teacher who comes in with a printed book filled with crooked marks, and would have it that learning must be thus acquired. Instead of continuing the natural process of instruction to the complete development and information of the mind, an abnormal method has been adopted by mankind with many hurtful consequences.

The youth at a certain age is led into the world of science, and there dismissed from the mother-method, to acquire, if he can, the painful and tedious use of meaningless hieroglyphics. There he must study with the eye, learning as best he may the significance of the crooked signs which can at the most signify no more than words. How much of human energy and life and thought have been thus wasted in the instruction of the mind by characters and symbols. The eyes of mankind have, as we said, been dimmed and shadowed, and at the same time the faculties have been overheated and the equipose of perception and memory seriously disturbed by this unnatural process of learning.

Human beings begin the acquirement of knowledge with words, and they end with words; but an unnatural civilization has taught man to walk the greater part of his intellectual journey by means of arbitrary systems of writing and printing. When the next Columbian Year arrives we shall see him untaught (a hard thing withal) and retaught on nature's plan of learning. Nature teaches language by sound only. Artificiality writes a scrawl. Nature's book is a book of words. Man's book is as yet a book of signs and symbols. Nature's book utters itself to the ear, and man's book blinds the eyes and overheats the imagination. Nature's method is to teach by the ear, and to reserve the sight for the discovery and enjoyment of beauty.

The sound-book in some form is coming; and with that the intellectual repose of mankind will begin to be restored. The use of the eye for the offices of education instead of the stronger ear, has, we think, impaired, if it has not destroyed, the equilibrium of the human mind. That equilibrium must be restored. The mental diseases and unrest of our race are largely attributable to the over-excitement of the faculties through ages of too much seeing.

The Age of Hearing is, we think, to be ushered in with the twentieth century. The coming of that age will tend to restore the mental balance of mankind. Memory, now almost obliterated, will come again. The over-heated perceptions will cool. The imagination will become calm, and the eye itself will recover, we hope, from the injuries, of overstrain, and will regain its power and lustre. Man will see once more as the eagle sees, and will learn Shakespeare by heart. He will remember all knowledge, and will again be able to see, as of old, from Sicily to Carthage!

THE EVOLUTION OF THE DYNAMO.

BY PROFESSOR JOSEPH P. NAYLOR, A.M.

It is difficult to estimate the influence in modifying and shaping the nineteenth century civilization that has resulted from the discovery of the dynamo and the production of heavy currents of electricity. That it has had great influence is evident without question. The arc light for out-of-doors lighting and the incandescent lamp for inside has modified all our previous ideas of illumination. Effects in light are now produced daily that were beyond imagination twenty years since. The trolley and the electromoter have largely solved the problem of rapid transit through our crowded cities. Thus larger business facilities, suburban homes and cheaper living, cleanliness and better sanitary conditions are electrical results.

The transmission of energy by the electric current from a central plant makes possible many small industries that could not exist without it, and gives employment and happiness to hundreds. The art of Electro-metallurgy seems but the development of months: yet it already employs millions of capital and is adding thousands daily to the world's wealth. Steam and wind and tide contribute to the work. Even Niagara is being touched by the spirit of the time and sends her wasting energy thrilling through the electric wires to turn the wheels of many busy factories. It is perhaps not the least remarkable fact in connection with this work that it is largely the product of the last thirty years, and that it had its very beginning less than seventy years since. Edison and Thompson and Brush are honorable household names; yet they are still living to produce even greater electric marvels. In fact, so rapid and brilliant has been the development that in the brilliancy some of the pioneers in the work have been almost forgotten, except by the specialist and the student, and it is no small part of this sketch to do them honor. The tiny spark of Faraday may be lost in the brilliancy of the million-candle-power search-light, yet the brilliancy of the search-light but enhances the wonder of the discovery of the spark.

The discovery of electro-magnetic induction marked the beginning of a new era; for in it lay all the possibilities of the future of electrical science. Michael Faraday, the third son of a poor English blacksmith, was born at Newington, Surrey, England, September 3, 1791. His father's health was never the best, and due to the resulting straitened circumstances his early education consisted of the merest rudiments of reading, writing and arithmetic. His early life was, no doubt, largely spent in the street; but at thirteen he became errand boy to a book-seller of London. About a year later he was apprenticed to a book binder, with whom he served seven years, learning the trade.

It was while an apprentice that Faraday began reading scientific articles on chemistry and physics in the books he was set to bind. He also tried to repeat the experiments of which he read. And more, he pondered over them long and earnestly, until he saw clearly the principles involved in them. It was in these early days of experimenting and self-education that the desire to become a philosopher was implanted in his mind. He embraced every chance for scientific study and caught every opportunity for intellectual self-improvement. In the last year of his apprenticeship he was enabled through the kindness of a customer at his master's shop, to attend a course of four lectures on chemistry, given by Sir Humphry Davy at the Royal Institution. This marked the turning point in his life. He made careful notes of the lecture, and afterward transcribed them neatly into a book and illustrated them with drawings of the apparatus used.

After completing his apprenticeship, Faraday began life as a journeyman bookbinder. He had, however, as he says, "no taste for trade." His love of science became a consuming desire that he sought in every way to gratify. Inspired by his longing for scientific pursuits, he sent his lecture notes to Sir Humphry Davy, with the request that if opportunity offered he would give him employment at the Royal Institution. Davy was favorably impressed with the lecture report, and sent a kindly reply to the young philosopher. Shortly after this a vacancy did happen to occur at the Institution, and upon the recommendation of Davy, Faraday was elected to the place. Thus, in 1813, in the humble capacity of an assistant charged with the simple duty of dusting and caring for the apparatus, Michael Faraday began the life that was destined to make him the first scientist of the world and to bring honor to the Institution which had given him his opportunity.

There is inspiration and encouragement to be found in reading the story of Faraday's success. He has been called a genius; but his genius seems to have largely consisted in persistent industry and the habit acquired in those early days of thinking over his experiments and reading until he had a clear perception of all there was in them. He lived in his work, and loved it. In the fifty busy years that followed his installment at the Royal Institution he digged deep into nature's secrets, and gave the world many brilliant gems as evidence of his industry. But of all his discoveries, electro-magnetic induction is the crowning masterpiece and that for which the world stands most his debtor.

The principle of conservation of energy, now so well known and universally accepted, was then but a vague guess in the minds of the more advanced in science. Faraday was among the first to accept the new doctrine, and many of his brilliant discoveries were made in his effort to prove the truth of these important generalizations. He was acquainted with Sturgeon's method of making magnets by sending a current of electricity through a wire wound around a bar of iron; and he reasoned, if electricity will make a magnet, a magnet ought to make electricity. As early as 1821 his note book contains this suggestion: "Convert magnetism into electricity." Again and again he attacked the problem; but it was not until the autumn of 1831 that his efforts to solve it were successful. Then in a series of experiments that have scarcely ever been equaled in brilliancy and originality, he gave to the world the principle on which is based the wonderful development of modern electrical science.

The principle is briefly stated. The space, around a wire carrying an electric current, or in the neighborhood of a magnet, has a directive effect upon a magnetic needle, and is hence called a magnetic field. 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 assured 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 passing 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 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 Roentgen 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 Roentgen, of Wuerzburg, made the discovery which seems likely to contribute so much to our knowledge of the mysterious processes of nature. On that day Dr. Roentgen 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 Roentgen 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. Roentgen himself called the phenomena the X, or unknown, rays.

In the experimentation referred to, Roentgen 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 Roentgen 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 Roentgen soon announced his discovery to the Physico-Medical Society of Wuerzburg. 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 Roentgen'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 Roentgen 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 Roentgen 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. Roentgen 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 Roentgen 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!



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 substitution 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 passed 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 analagous 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 assiduity. 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 classes 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. One disease after another was investigated. It was demonstrated in the case of both the lower animals and men that a large number of maladies and plagues might be completely disarmed of their terrors by the process of inoculation. The name of Pasteur became more and more famous. The celebrated Pasteur Institute was founded at Paris, under the patronage of the French Government, and in some sense under the patronage of the whole world. To this establishment diseased subjects were taken for treatment, and here experimentation was carried on over a wide range of facts.

The value of the results attained can hardly be overestimated. The fear which mankind have long entertained on account of plagues and epidemics, and the loss which the animal industries of the world have sustained, were largely abated. As yet the use of the Pasteur methods for the prevention and cure of disease is by no means universal; but the knowledge which has come of his investigations and of the results of them has diffused itself among all civilized nations, and the hygienic condition of almost every community has been most favorably affected by the new knowledge which we possess of bacteria and of the means of destroying them.

Pasteur, whose recent death has been mourned by the best part of mankind, was an explorer and forerunner. His industry in his chosen field of investigation was prodigious. When he was already nearly seventy years of age, he undertook the investigation of hydrophobia, with the purpose of discovering, if he might, the germ of that dreaded disease, thus preparing a method for inoculation against it.

Hydrophobia is one of the most subtle diseases ever known. So obscure and uncertain are its phenomena that many able men have been led to doubt the existence of such a disease! The mythological origin of the malady in the supposed influence of a dog-star seemed to strengthen the view that hydrophobia, as a specific disease, does not exist. It is undeniably true that the great majority of the cases of so-called rabies are pure myths. Under investigation they melt away into nothing but alarm and fiction. However, there appeared to be a residue of actual hydrophobia, though the disease as tested by its name exists in fancy rather than fact.

In any event, Pasteur began to investigate hydrophobia, and at length discovered the bacilli which produce it. At least he found in animals affected with rabies, notably in the spinal marrow of such animals, minute living organisms, having the form of thread-like animalculae, with heads at one end. The microscope showed also among these thread-like bodies other organisms that were like small circular black specks, or disks.

The next step in the work was to test the result by inoculating a well animal with these bodies. Pasteur selected rabbits for his experimentation. When the experiment was made, the inoculated rabbit was presently attacked with the disease, and soon died in spasms. The repetition of the experiment was attended with like results.

The philosopher next tried his established method of domesticating, or attenuating, the poison. The spinal cord of a rabid dog was obtained, and with this the first rabbit was inoculated. In about two weeks it took hydrophobia. Hereupon the spinal cord was extracted, and the second rabbit was inoculated; then the third; then the fourth, and so on. It was observed, however, that at each stage the intensity of the disease was in this way strangely increased; but the period of inoculation became shorter and shorter.

It was next found that by preserving the spinal cords of the animals that had died of the disease—by preserving them in dry tubes—the poison gradually lost its power. At last the virus seemed to die altogether. Then the experiment of inoculating against the disease was begun. A dog was first inoculated with dead virus. No result followed. Then he was inoculated with stale virus, and then with other virus not so stale. It was found that by continuing this process the animal might be rendered wholly insusceptible to the disease.

The next step was the human stage of experimentation. It was in July of 1885 that Pasteur first employed his method on a human subject. A boy had been bitten and lacerated by a rabid dog. The inoculation was thought to prove successful. Soon afterward some bitten children were taken from the United States to Paris, and were treated against the expected appearance of hydrophobia. Others came from different parts of the continent. Within fourteen months more than two thousand five hundred subjects were treated, and it is claimed that the mortality from hydrophobia was reduced to a small per cent of what it had been before.

It should be said, however, that neither have the results arrived at by Pasteur respecting the character of rabies been so clear, nor have his experiments on subjects supposed to be poisoned with the disease been so successful as in the case of other maladies. It remains, nevertheless, to award to Louis Pasteur the first rank among the bacteriologists of our day, as well as a first place among the philanthropists of the century. Only Robert Koch, of Germany, is to be classed in the same list with him.

KOCH'S BATTLE WITH THE INVISIBLE ENEMY.

There was a great negative reason for the success of the World's Columbian Exposition. The cholera did NOT come! It is quite true that there is no if in history; but IF the cholera had come, IF the plague had broken out in our imperial Chicago, what would have become of the Columbian Exposition? Certainly the Man of Genoa would have had to seek elsewhere for a great international gathering in his honor.

The cholera did not arrive, although it was expected. The antecedent conditions of its coming were all present; but it came not. The American millions discerned that the dreaded plague was at bay; a feeling of security and confidence prevailed; the summer of 1893 went by, and not a single case of Asiatic cholera appeared west of the Alleghenies. We are not sure that a single case appeared on the mainland of North America. And why not?

It was because the increasing knowledge of mankind, reinforced with philanthropy and courage, had drawn a line north and south across Western Europe, and had said, Thus far and no farther. Indeed, there were several lines drawn. The movement of cholera westward from the Orient began to be obstructed even before it reached Germany. It was obstructed in Italy. It was obstructed seriously on the meridian of the Rhine. It was obstructed almost finally at the meridian of London. It was completely and gloriously obstructed at the harbor of New York.

Civilization has never appeared to a better advantage than in the building of her defences against the westward invasion of cholera. There have been times within two decades of the present when in the countries east of the Red Sea 3000 people have died daily of the Asiatic plague. Egypt has been ravaged. The ports of the Mediterranean have been successfully invaded. Commerce, reckless of everything except her own interests, has taken the infection on shipboard, and sailed with it to foreign lands, as though it were a precious cargo! Importers, anxious for merchandise, have stood ready to receive the plague, and plant it without regard to consequences. But in the midst of all this, a new power has arisen in the world, and standing with face to the east, has drawn a sword, before the circle of which even the spectral shadow of cholera has quailed and gone back! Humanity might well break out in rhapsody and jubilee over this great victory.

Among the personal agencies by which cholera has been excluded from Europe and America, first and greatest is Dr. Robert Koch, of Berlin. He, more than any other one man, has contributed to the glorious exemption. Dr. Koch, now by the favor of his Emperor, Baron Koch, is one of those heroic spirits who go before the human race exploring the route, casting up a highway and gathering out the stones. Thus shall the feet of the oncoming millions be not bruised and their shouts of joy be not turned to lamentation.

Robert Koch was born at Klausthal, in the Hartz mountains, on the eleventh of December, 1843. He is a German of the Germans. In his youth he was a student of medicine at Goettingen, where at the age of twenty-three he took his first degree. He was by nature and from his boyhood a devotee of science. For about ten years he practiced his profession, but continued his studies with indefatigable zeal. The investigations of Pasteur had already filled Europe with applause when Koch, following on the same lines of scientific exploration, began to enlarge the borders of knowledge. He became a bacteriologist of the first rank. He began to investigate the causes and nature of contagion; but as late as 1876 his name was still unknown in the cyclopaedias.

Koch was twenty-one years the junior of Pasteur; but his enthusiasm and genius now bore him rapidly to a fame as great as that of his predecessor. His first remarkable achievement was a demonstration of the cause and cure of splenic fever in cattle. He showed, just as Pasteur had done in similar cases, that the plague in question was due to the specific poison of a bacterium, and that the disease might be cured by inoculation against it. This he proceeded to do, and the demonstration and good work brought him to the attention of the old Emperor. Dr. Koch was made a member of the Imperial Board of Health in Berlin.

A greater discovery was already at the door. Dr. Koch began a careful investigation into the nature of consumption. His discovery of the germ of splenic fever, and that of chicken cholera, as well as the general results in this direction in other laboratories of Europe, led him to the conjecture that consumption also is a zymotic or bacterial disease. His inquiry into this subject began in 1879, and extended to March of 1882. On that day, in a paper before the Physiological Society of Berlin, he announced the discovery of the tubercle bacillus. He was able to demonstrate the existence of the germ of consumption, and to describe its methods of life, as well as the character of his ravages.

Here then at last was laid bare the true origin of the most fatal disease which has ever afflicted mankind. He who has not informed himself with respect to the almost universal prevalence of consumption among the nations of the earth, or taken note of the mortality from that dreaded enemy, by which nearly one-sixth of the human race sooner or later perishes, will not have realized the awful character of this enemy. To attack such a foe, to force him into a corner, even as Siegfried did the Grendel in his cavern, was an achievement of which the greatest of mankind might well be proud.

The discovery of the bacillus of consumption by no means assured the cure of the disease; but it foretokened the time when a cure would be found. This prophecy, though it has not yet been clearly fulfilled, is, in the closing years of the century, in process of fulfillment. The enemy does not readily yield; but such has been the gain in the contest that already within the last twenty years the mortality from consumption of the lungs has fallen off more than forty per cent! Much of this gain has been made by the reviving confidence of human beings that sooner or later tuberculosis would be destroyed. Hygiene has done its part; and other circumstances have conduced to the same result. Though neither Dr. Koch nor any other man living has been able as yet positively to meet and vanquish consumption in open battle, yet the goblin has in a measure been robbed of his terrors. He is no longer boastful and victorious over the human race.

After the discovery of the tubercle bacillus, the fame of Robert Koch became world-wide. In the following year he was made a privy councilor, and was placed in charge of an expedition organized by the German government to go into Egypt and India for the investigation of the causes of Asiatic cholera. The expedition was engaged in this work for nearly a year. Koch pursued his usual careful method of scientific experimentation. He exposed himself to the contagion of cholera, but his science and fine constitution stood him well in hand, and he returned unharmed.

It was in May of 1884 that he was able to announce the discovery of the coma bacillus, that is, the bacterium of cholera. Here, again he had the enemy at bay. For long ages the Asiatic plague had ravaged the countries of the East with little hindrance to its spread or fatality. The disease would appear as an epidemic at intervals and sweep all before it. The wave of death would roll on westward from country to country, until it would subside, as if by exhaustion, in the far west. Two or three times within the century cholera had been fatally scattered through American cities. It had spread westward along the rivers of the Ohio and Mississippi valleys, and into country districts, where villages and hamlets were decimated.

The discovery of Koch was a virtual proclamation that this ruin of mankind from the Asiatic plague should cease. The knowledge that the disease was due to a living bacterium, that without the germ and the spread of the germ the plague could not exist, was a virtual announcement that in the civilized countries it should not any longer exist.

The discoverer was now set high in the estimation of mankind. Imperial Germany best of all countries rewards its benefactors. France is fascinated with adventure; Great Britain with slaughter; America with bare political battles; but Germany sees the true thing, and rewards it. Koch was immediately placed beyond want by his government, and titles and honors came without stint.

The Empire would fain have such a man at the seat of power. Dr. Koch was, in 1885, made a professor in the University of Berlin. The new chair of Hygiene was created for him, and he was made Director of the Hygienic Institute. It was in this capacity that armed with influence and authority and having the resources of the government virtually at his disposal, he directed in the great scientific work by which a bulwark against cholera was drawn almost literally across Europe, and was defended as if with the mounted soldiery of science and humanity. True enough, cholera managed to plant itself in Italy in 1886, and in Hamburg in 1892, and the plague was scattered into several German towns. But it came to Hamburg by water, not by land. It did there during the summer a dreadful work, but the battle was the Waterloo of the enemy. Not again while the present order continues will it be possible for the dreaded epidemic to get the mastery of a great German city.

It was to be anticipated that Dr. Koch's discovery of the tubercle bacillus would lead him on to the discovery of a cure for tuberculosis. Very naturally his thought on this subject was borne in the direction of inoculation. That method had been used by Pasteur and by himself in the case of other infectious diseases. Why should it not be employed in consumption? If the "domestication," so-called, of the virus of splenic fever and the use of the modified poison as an antiseptic preventive of the disease was successful, as it had been proved to be, why should this not be done with the attenuated virus of consumption?

The last five years of the ninth decade were spent by Dr. Koch in experimentation on this subject. He found that the tubercular poison might be treated in the same manner as the poison of other infectious diseases. He experimented with methods for domesticating the bacillus of consumption, and reached successful results. On the fourteenth of November, 1890, he published in a German medical magazine at Berlin a communication on a possible remedy for tuberculosis. He had prepared a sort of lymph suitable for hypodermic injection, and with this had experimented on a form of external tuberculosis called lupus. This disease is a consumption of the skin and adjacent tissues. It is a malady almost as dreadful as consumption of the lungs, but is by no means frequent in its occurrence. It is found only at rare intervals by the medical practitioner.

Dr. Koch had demonstrated that lupus is a true tuberculosis—that the germ which produces it is the same bacillus which produces consumption of the lungs. He accordingly directed his effort to cases of lupus, treating the patients with hypodermic injections which he had prepared from the modified form of the tubercular poison. He was successful in the treatment, and was able to announce, to the joy of the world, that he had discovered a cure for lupus; and the announcement went so far as to express a belief in the salutary character of the remedy in the treatment of consumption of the lungs.

Dr. Koch, however, with the usual caution of the true men of science, did not announce his tuberculin, or lymph, as a cure for pulmonary consumption. He did not even declare that it was positively a remedy for the other forms of tuberculosis, but did announce his cure of cases of lupus by the agent which he had prepared. The world, after its manner, leaped at conclusions, and the newspapers of two continents, in their usual office of disseminating ignorance, trumpeted Koch's discovery as the end of tubercular consumption.

In January of 1891, Dr. Koch published to the world the composition of his remedy. It consists of a glycerine extract prepared by the cultivation of tubercle bacilli. The lymph contains, as it were, the poisonous matter resulting from the life and activity of the tubercle bacterium. The fluid is used by hypodermic injection, and when so administered produces both a general and local reaction. The system is powerfully affected. A sense of weariness comes on. The breathing is labored. Nausea ensues; and a fever supervenes which lasts for twelve or fifteen hours. It is now known that the action of the remedy is not directly against the tubercle bacilli, but rather against the affected tissue in which they exist. This tissue is destroyed and thrown off by the agency of the lymph; being destroyed, it is eliminated and cast out, carrying with it the bacteria on which the disease depends.

The results which have followed the administration of Koch's lymph for consumption of the lungs have not met the expectation of the public; but something has been accomplished. Ignorant enthusiasm has meanwhile subsided, and scientific men in both Europe and America are pressing the inquiry in a way which promises in due time the happiest results.

ACHIEVEMENTS IN SURGERY.

It will not do to disparage the work of the ancients. The old world, long since fallen below the horizon of the past, had races of men and individuals who might well be compared with the greatest of to-day. In a general way, the ancients were great as thinkers and weak as scientists. They were great in the fine arts and weak in the practical arts. This is true of the Hindus, the Egyptians, the Greeks, the Romans, even of the Aztecs and the Peruvians.

The art work of these old peoples, whether in sculpture, painting or poetry, surpassed, if it did not eclipse, corresponding periods of modern times. In some of the practical arts the old races were proficient. In architecture, which combines the aesthetic and practical elements, the man of antiquity was at least the equal of the man of the present. In one particular art—a sort of humanitarian profession based on natural science and directed to the preservation of life—the ancients had a measure of proficiency. This art was surgery. The surgeon was even from the beginning, and he will no doubt be even to the end.

The great advance which has been made in surgical science and practice is shown in two ways: first, in a great increase of courage, by which the surgeon has been led on to the performance of operations that were hitherto considered rash, audacious or impossible; and secondly, by the immunity which the surgeon has gained in the treatment of wounds through the increased knowledge he possesses of putrefaction and the means of preventing it. It were hard to say whether the surgeon's increase of skill and courage in performing operations has equalled his increased skill in the after treatment of wounds.

These improvements have all proceeded from scientific investigation. They have come of the application of scientific methods to the treatment of surgical diseases. With the investigations of Pasteur and the development of the science of bacteriology, it was seen at a glance how large an influence such investigation must have in the work of the surgeon. The publication of Tyndall's "Essays on the Floating Matter of the Air in Relation to Putrefaction and Infection," in 1881, gave a great impulse to the new practice; but that practice had been already confirmed by the great and original work of Sir Joseph Lister, an English surgeon who as early as 1860 had introduced the antiseptic method of bandaging.

It is within the last forty years that the greatest marvels of modern surgery have been performed. It would seem that no part of the human body is now beyond the reach of surgical remedy. Almost every year has witnessed some new and daring invasion of the fortress of life with a view to saving it. Old opinions with respect to what parts of the human economy are really vital have been abolished; and a new concept of the relation of life to organism has prevailed.

Until recently it was supposed that the peritoneal cavity and the organs contained therein, such as the stomach, the liver, the bowels, etc., could not be entered by the surgeon without the certain result of death. To do so at the present time is the daily experience in almost every great hospital. The complexity of civilization has inflicted all manner of hurts on the human body, and the malignity of disease has spared no part. It was supposed that the cranial cavity could not be entered or repaired without producing fatal results. It was taken for granted that certain organs could not be touched, much less treated capitally, without destroying the subject's life. But one exploration has followed another and one successful adventure has been succeeded by another still more successful until the surgeon's work is at the present time performed within a sphere that was until recently supposed to be entirely beyond his reach.

As to the liver, that great organ is freely examined and is treated surgically with considerable freedom. This is true also of the stomach, which until recently was supposed to be entirely beyond the surgeon's touch. Within the last two decades sections of the stomach have been made and parts of the organ removed. Not a few cases are recorded in which subjects have fully recovered after the removal of a part of the stomach. Sections of the intestinal canal have also been made with entire success. Several inches of that organ have in some cases been entirely removed, with the result of recovery! The spleen has been many times removed; but it has been recently noted that a decline in health and probably death at a not distant date generally follow this operation.

The disease called appendicitis has either in our times become wonderfully frequent or else the improved methods of diagnosis have made us acquainted with what has long been one of the principal maladies of mankind. The appendix vermiformis seems to be a useless remnant of anatomical structure transmitted to us from a lower animal condition. At least such is the interpretation which scientists generally give to this hurtful and dangerous tube-like blind channel in connection with the bowels. That it becomes easily inflamed and is the occasion of great loss of life can not be doubted. Its removal by surgical operation is now regarded as a simple process which even the unlearned surgeon, if he be careful and talented, may safely perform. The surgical treatment of appendicitis has become so common as to attract little or no notice from the profession. Even the country neighborhood no longer regards such a piece of surgery as sensational.

The use of surgical means in the cure, that is the removal, of tumors, both external and internal, has been greatly extended and perfected. The surgeon now carries a quick eye for the tumor and a quick remedy for it. In nearly all cases in which it has not become constitutional he effects a speedy cure with the knife. The cancerous part is cut away. It has been observed that as the recent mortality from consumption has decreased cancerous diseases have become more frequently fatal. Whether or not there be anything vicarious in the action of these two great maladies we know not; but statistics show that since the beginning of Pasteur's discoveries the one disease has diminished and the other increased in almost a corresponding ratio. Meanwhile, however, surgery has opposed itself not only to cancers but to all kinds of tumors, until danger from these sores has been greatly lessened. The removal of internal tumors such as the ovarian, is no longer, except in complicated and neglected cases, a matter of serious import. Such work is performed in almost every country town, and the amount of human life thus rescued from impending death is very great. The work of lithotomy is not any longer regarded with the dread which formerly attended it. In fact, every kind of disease and injury which in its own nature is subject to surgical remedy has been disarmed of its terror. The eye and the ear and all of the more delicate organs have become subject to repair and amendment to a degree that may well excite wonder and gratify philanthropy.