INVENTION OF PHONOGRAPH BY EDISON--SCOTT'S PHONAUTOGRAPH-- IMPROVEMENTS OF BELL AND TAINTER--THE GRAPHOPHONE--LIBRARY OF WAX CYLINDERS--THE GRAMOPHONE.

Following closely upon the discovery of the telephone the phonograph came, literally speaking for itself, and adding another surprise to the wonderful inventions of that prolific period. It was in the latter part of 1877 that Thomas A. Edison showed to a few privileged friends a modest looking little machine. He turned the crank, and to the astonishment of those present it said. "Good morning! How do you do? How do you like the phonograph?" Its voice was a little metallic, it is true, but here was presented an insignificant looking piece of mechanism which was undeniably a talking machine and one with an unlimited vocabulary. So-called talking machines had been made before, of which the Faber machine was a type. These, by an arrangement of bellows to furnish air, and flexible pipes in imitation of the larynx and vocal organs, made laborious and wheezy efforts to imitate the mechanical functions of the throat and tongue in articulate speech, but the method was fundamentally faulty and no success was attained. Edison followed no such leading. His phonograph made no attempt at imitating in construction the complex organization of the human throat, but was as wonderful in its divergence therefrom and in its simplicity as it was in the success of its results. The machine was patented by him Feb. 19, 1878, No. 200,521, and its life principle is simply and clearly defined in the first claim of the patent, as follows:

"The method herein specified of reproducing the human voice, or other sounds, by causing the sound vibrations to be recorded substantially as specified, and obtaining motion from that record as set forth for the reproduction of sound vibrations."

The invention was a striking and interesting novelty and at once attracted the attention of scientific men as well as the general public.

Its first public exhibition was about the latter part of January, 1878, before the Polytechnic a.s.sociation of the American Inst.i.tute, at New York. It spoke English, French, German, Dutch, Spanish and Hebrew with equal facility. It imitated the barking of a dog and crowing of a c.o.c.k, and then catching cold, coughed and sneezed and wheezed until it is said a physician in the audience proposed sending a prescription for it. It was also suggested by an irreverent man that it might take the place of preachers in the rendition of sermons, while another thought that as it reproduced music with equal facility it might take the place of preacher and choir both. In the spring of 1878 it was exhibited at Washington by Edison and his a.s.sistant, Mr. Batchelor. Mr. Edison was the guest of Mr.

U. H. Painter, and in his parlors it was shown to a party of gentlemen.

From Mr. Painter's house the machine was taken to the office of the a.s.sistant Secretary of the Interior, thence to the Academy of Sciences, in session at the Smithsonian Inst.i.tution, and at night it was taken to the White House and exhibited to President and Mrs. Hayes.

[Ill.u.s.tration: FIG. 189.--FIRST PHONOGRAPH.]

The form of the first phonograph is shown in Fig. 189. It consisted of three princ.i.p.al parts--the mouthpiece A, into which speech was uttered, the spirally grooved cylinder B, carrying on its periphery a sheet of tin foil, and a second mouthpiece D. The cylinder B and its axial shaft were both provided with spiral grooves or screw threads of exactly the same pitch, and when the shaft was turned by its crank its screw threaded bearings caused the cylinder to slowly advance as it rotated.

The mouthpiece A had adjacent to the cylinder a flexible diaphragm carrying a little point or stylus which bore against the tin foil on the cylinder. When the mouthpiece A was spoken into and the cylinder B was turned, the little stylus, vibrating from the voice impulses, traced by indentations a little jagged path in the tin foil that formed the record. To reproduce the record in speech again, the mouthpiece A was adjusted away from the cylinder, the cylinder run back to the starting point, and mouthpiece D was then brought up to the cylinder. This mouthpiece had a diaphragm and stylus similar to the other one, only more delicately constructed. This stylus was adjusted to bear lightly in the little spiral path in the tin foil traced by the other stylus, and as the tin foil revolved with the cylinder its jagged irregularities set up the same vibrations in the diaphragm of mouthpiece D as those caused by the voice on the other diaphragm, and thus translated the record into sounds of articulate speech, exactly corresponding to the words first spoken into the instrument. In Fig. 190 is shown a further development of the phonograph, in which a single mouthpiece with diaphragm and stylus serves the purpose both of recorder for making the record and a speaker for reproducing it, a trumpet or horn being used, as indicated in dotted lines, to concentrate the vibrations in recording and to augment the sound in reproducing.

[Ill.u.s.tration: FIG. 190.--SECOND FORM OF PHONOGRAPH.]

The phonograph is in reality a development of the phonautograph, which was an instrument invented by Leon Scott in 1857 to automatically record sounds by diagrams. There is a model of Scott's phonautograph in the National Museum at Washington, D. C, and it consists of a chamber to catch the sound waves and an elastic diaphragm with stylus working on a revolving cylinder bearing a sheet of paper coated with lampblack. The phonograph's record-making mouthpiece, with its diaphragm and stylus, is substantially a phonautograph, but instead of simply causing the stylus to trace a record on carbon-coated paper and stopping with this result, Edison traced a record in a substance--tinfoil--which was capable of mechanically translating that record into sound again by a mere reversal of the function of the stylus and diaphragm. This was the very essence of simplicity and logical reasoning. All records had been heretofore traced for visual inspection only. Edison's record was not for visual inspection, but was endowed with the mechanical function of reproducing sound.

From the first Edison believed that his phonograph was to fill an important place in the business activities of the world, since here seemed a silent but faithful stenographer which reproduced the words of the speaker with absolute fidelity, even to the quality of emphasis and inflection, and which made no mistakes, was always even with the speaker in its work, and asked no questions. For a number of years, however, the invention lay dormant and served no other purpose than that of a scientific curiosity or an amusing toy. The difficulty of its practical application largely existed in the perishable form of the record, which, being in tinfoil, was liable to be mutilated and distorted, and was not well adapted for storage or transportation.

A few years after the announcement of Mr. Edison's invention. Dr.

Alexander Graham Bell, the distinguished inventor of the telephone, with his a.s.sociates, Messrs. Chichester A. Bell and Charles Sumner Tainter, directed their attention to the improvement of the phonograph. Dr. Bell had received from the French government, upon the recommendation of the French Academy of Sciences, the Volta prize of 50,000 francs as a recognition of his successful work in acoustics and the invention of the telephone, and with this sum he built the Volta Inst.i.tute in Washington and carried on the work of developing the phonograph.

On May 4, 1886, Chichester A. Bell and Sumner Tainter obtained patents Nos. 341,214 and 341,288, which covered a great improvement in the record of the phonograph. This invention subst.i.tuted for the tinfoil sheet a surface of wax, which was finally fashioned into a cylinder, and instead of merely indenting the record on tinfoil the stylus cut a distinct groove or kerf in the wax cylinder as it revolved, dislodging therefrom a minute filament or shaving and forming a record which was not only far more positive in its translating effect and more easily transported and stored, but was also less perishable, and besides it could be easily effaced without loss of the cylinder by simply smoothing off the surface of the cylinder again when it was desired to make a new record. This invention quickly grew into practical use, and is known as the "Graphophone."

[Ill.u.s.tration: FIG. 191.--THE GRAPHOPHONE, RECORDING AND REPRODUCING DEVICES.]

In Fig. 191 is shown on the left a cross section of the diaphragm, recording stylus, and wax cylinder, of the graphophone, the stylus plowing a tiny groove in the wax cylinder in the act of recording the speech, and on the right is shown the reproducing stylus traversing the record groove in the wax cylinder, and the diaphragm chamber with which the ear tubes are connected. The grooves in the wax, although giving forth mechanical movement that is translated into sound, are very minute, being only 6/10,000 of an inch deep.

When the possibilities of the graphophone became known, capital was quickly supplied for its commercial exploitation, and the Columbia Phonograph Company was organized. At the present time, owing to the great increase in the business, the control of the graphophone business is vested in two branches, the Columbia Phonograph Company, which has charge of the selling, and which has offices throughout all the princ.i.p.al cities of this country and some of the larger ones of Europe, and the American Graphophone Company, which attends to the manufacturing branch, and whose factory is located at Bridgeport, Conn., where, it is said, that in 1898 the production of the factory reached the point of one graphophone for every minute of the day, making a total daily output of 600 machines. Although the Bell and Tainter patents of 1886 represent the basic principles of the graphophone, its development and perfection have been contributed to in many subsequent improvements by Messrs.

Bell, Tainter, McDonald, and others. The more important of these are covered by patents No. 375,579, Dec. 27, 1887; No. 380,535, April 3, 1888; No. 527,755, Oct. 16, 1894, and No. 579,595, March 30, 1897.

At the beginning of this industry it was thought that the princ.i.p.al use of the instrument would be found in business applications, to take the place of the stenographer, but it proved difficult to revolutionize office methods, especially as the earlier machines were somewhat intricate, and the business man had no time to divide in engineering a machine. These difficulties, however, have been so far overcome by modern improvements and simplification of the machine that its use in business houses as an amanuensis has become quite common. The greatest use of the graphophone is, however, for amus.e.m.e.nt purposes. Its songs, orchestral and solo renditions, and its humorous monologue reproductions const.i.tute to-day a great library of wax cylinders, regularly catalogued and sold by the thousands. It will readily be understood that the formation of the cylinders must const.i.tute a great business of itself when it is remembered that many record cylinders accompany each graphophone, and that the latter are turned out at the rate of one a minute by a single company. Many thousands of these cylinders are made daily. Some are sent out simply as plain wax cylinders, onto which the records are made by the voice of the purchaser, while others have records made for them of popular music, monologues in dialect, humorous speeches, etc. The waxy composition, which is in reality a species of soap, is melted in huge pots, and then pa.s.ses from one floor to another, undergoing a refining process in its progress, and finally reaches the molds. These molds are arranged in rows around a horizontal wheel about eight feet in diameter. The wheel is kept revolving, and a man on one side is kept constantly busy in filling the molds with the molten material as they reach him. A half revolution of the wheel brings the filled molds to the other side of the room, and by that time the material has hardened sufficiently to enable another attendant, stationed there, to remove the cylinders from the molds. Thus the wheel is kept going, receiving at one side a charge of the melted wax and discharging at the other molded cylinders, which are afterwards turned true on the surface. The record-making department is both unique and interesting. Here the records of music are produced, and they are made by bands and performers engaged for the purpose, many of which, operating at the same time, produce such a medley as to be scarcely distinguishable to the visitor. The records are tested by about half a hundred women, each of whom has a little compartment or booth framed in by gla.s.s part.i.tions. The duty of the tester is to decide upon the merits of the record by actually listening to it on the graphophone.

A very important feature in record-making, from a commercial standpoint, is in means for cheaply duplicating records. If every record cylinder had to be made by the separate act of a performer such records would be very expensive. An original record is first made by some celebrated musician or speaker, and this record is afterwards multiplied and reproduced in large numbers. For this purpose an original record by suitable mechanism is made to take the place of the speaker or singer, and so multiplies and reproduces the original record. The duplicating of records was contemplated by Edison from the first, as seen in his British patent, 1,644 of 1878, and later appliances for accomplishing such results are covered under Tainter's patent, No. 341,287, Bettini's, No. 488,381, and McDonald's, No. 559,806. The diaphragms used in the recorders and reproducers are made of French rolled plate gla.s.s, thinner than a sheet of ordinary writing paper. The recording stylus is shaped like a little gouge to cut the little grooves in the wax, while the corresponding stylus of the reproducer has a ball-shaped end to travel in the groove. Both the recording stylus and reproducing ball are made of sapphire, chosen on account of its hardness, to resist the great frictional wear to which they are subjected. When a record is to be effaced from a cylinder, it is turned off smooth on a sort of lathe, and the cutting tool or knife for this purpose is also made of sapphire.

The latest, loudest, and most impressive form of the talking machine is the "Graphophone Grand." This has a horn attachment exceeding the big horn of a bra.s.s band in size, and the wax cylinder is about four inches in diameter. Its reproductions in music and speech are so full and strong as to be clearly heard at the most remote part of a large hall, and its versatile voice lends effective rendition to all sorts and kinds of sounds, from the inspiring chords of "A Choir Invisible" to the grandiloquent and facetious rattle of a noisy and hustling auctioneer.

[Ill.u.s.tration: FIG. 192.--MODERN PHONOGRAPH.]

It is not to be understood, however, that the graphophone is the only speaking machine on the market, for about 250 patents have been granted on phonographs and graphophones. The National Phonograph Company, under many later patents granted to Mr. Edison, manufactures and sells the phonograph shown in Fig. 192, which is a very ingenious and effective instrument. This modern form of phonograph is actuated either by electricity or spring power, is regulated by a speed governor, and bifurcated ear tubes connect with the diaphragm case, which tubes are placed in the ears when the instrument is operated.

[Ill.u.s.tration: FIG. 193.--THE GRAMOPHONE RECORDER.]

The gramophone is also another speaking machine. This is the invention of Mr. E. Berliner and covered by him in patent No. 372,786, Nov. 8, 1887. An ill.u.s.tration of the gramophone recorder is given in Fig. 193.

Instead of a wax cylinder this machine employs a flat disc on which the record is formed as a volute spiral groove, gradually drawing toward the center. It is produced as follows: A zinc disc is covered by a thin film of acid resisting material, such as wax or grease, and is placed in a horizontal pan, mounted to revolve as a turn table about a vertical axis. A stylus and diaphragm, with speaking tube attached, are arranged above the disc, and when spoken into the vibrations of the diaphragm cause, through the stylus, a record to be traced through the wax, down to the zinc. As the waxed disc and pan are revolved, the stylus and diaphragm are gradually moved by gears toward the center of the disc.

While the record is being traced the waxed disc is kept flooded with alcohol from a gla.s.s jar, seen in the cut, to soften the film and prevent the clogging of the stylus. The disc, when completed, is then rinsed off and etched with acid, chromic acid being used, to prevent liberation of hydrogen bubbles. The etched disc is then electrotyped to form a matrix, and from this electrotype hard rubber duplicates of the original record are molded, which are capable of giving 1,000 reproductions. These rubber discs are placed on the reproducing instrument, which is arranged to cause the stylus to freely trail along in the spiral groove, and when the disc is rotated under the said stylus its record is converted into articulate speech. Such flat disc records give quite loud reproductions, are not easily destroyed, and may be compactly stored and transported. In the gramophone the diaphragm stands at right angles to the record disc and the stylus does not vibrate endwise to make a path of varying depth, as in the phonograph and graphophone, but the stylus vibrates laterally and traces a little zigzag line.

The cost of a talking machine is from $5 to $150. The wax cylinders cost from 25 cents to $3.00, and the cylinders will hold a record of from 800 to 1,200 words, equivalent to about three or four pages of print in an octavo volume. An important part of such machines is the motor, which must maintain a uniform rate of speed, and much ingenuity has been displayed on this part of the machine. Probably the largest use of the phonograph or graphophone is for home amus.e.m.e.nt and exhibition purpose.

The coin operated, or "nickel-in-the-slot" machine, finds a popular demand, while its utilitarian use as an amanuensis, or stenographer, is as yet a subordinate one.

Although twenty-one years of age, and of full growth, the phonograph is ever a wonderfully new and impressive device. When listening to it for the first time the conflict of emotions which it excites is difficult to a.n.a.lyze. A voice full of human quality, of clear and familiar enunciation, and speaking in the most matter of fact way about the most matter of fact things, proceeds from an insignificant and insensible bit of metal, presenting the apparently anomalous condition of speech without a speaker. When convinced that there is no trick, astonishment struggles with admiration and a desire for a personal introduction. We speak into it, and have the unique experience of listening to our own voice emanating from a different part of the room, instead of our own mouths. It is really difficult to believe one's own senses, and no wonder that it inspires the superst.i.tious with a feeling of awe. If Mr.

Edison had lived a few centuries earlier, and had produced such an instrument, his life might have paid the penalty of his ingenuity, for without doubt he would have been cla.s.sed as a wizard, and of close kin to the evil one.

The phonograph is the truth-telling and incontrovertible witness whose memory is never at fault, and whose nerves are never discomposed by any cross-examination. As evidence in court its word cannot be doubted, and the witness confronted by his own utterances from the phonograph must yield to its infallible dictum. The dying father, unable to write, may dictate to it his last will and testament, and leave a message for his loved ones, and long after the sod is green on his grave, that message would still be audible, and fresh and true to all the tender inflections of the heart's emotions. By its aid the Holy Father, at Rome, may give his personal and audible blessing to his children throughout the world, though separated by thousands of miles. Who can tell what stories of interesting and instructive knowledge would be in our possession if the phonograph had appeared in the ages of the past, and its records had been preserved? The voices of our dead ancestors, whose portraits hang on the wall, and the eloquent words of Demosthenes and Cicero would be preserved to us. In fact, we should be brought into vocal contact with the world's heroes, martyrs, saints, and sages, and all the great actors and teachers whose personalities have made history, and whose teachings have given us our best ideals. But perhaps the most practical and best characterization of the phonograph is given in Mr. Edison's own terse words. He says: "In one sense it knows more than we know ourselves, for it retains the memory of many things which we forget, even though we have said them. It teaches us to be careful of what we say, and I am sure makes men more brief, more businesslike, and more straightforward."

CHAPTER XXIII.

OPTICS.

EARLY TELESCOPES--THE LICK TELESCOPE--THE GRANDE LUNETTE--THE STEREO-BINOCULAR FIELD GLa.s.s--THE MICROSCOPE--THE SPECTROSCOPE-- POLARIZATION OF LIGHT--KALEIDOSCOPE--STEREOSCOPE--RANGE FINDER-- KINETOSCOPE AND MOVING PICTURES.

"And G.o.d said, Let there be light: and there was light. And G.o.d saw the light that it was good; and G.o.d divided the light from the darkness."

Thus early in the account of the creation is evidenced man's appreciation of the value of vision. Of all the senses which place man in intelligent relation to his environment none is so important as sight. More than all the others does it establish our relation to the material world. When the babe is born, and its little emanc.i.p.ated soul is brought in contact with the world, its wondering gaze sees the panorama of visible things touching its eyes, and it stretches forth its tiny arms in the vain effort to pluck the stars, apparently within its reach. Distance and time add their values to light and vision, and as his life expands to greater fullness, the perspective of his existence creeps into his consciousness, and he finds himself farther away, but still peering beyond into the infinity of distance, searching for the visible evidence of knowledge. From the earliest times man learned to spurn the groveling things of earth, and to delight his soul with the marvelous infinity of the sky and its heavenly bodies. _Nunc ad astra_ was his ambitious cry, and in no field has his quest for knowledge been more skillfully directed, faithfully maintained, or richly rewarded than in the study of astronomy. Many important discoveries in this field have been made in the Nineteenth Century, among which may be named the discovery of the planet Neptune by Adams, Leverrier and Galle in 1846; the satellites of Neptune in 1846, and those of Saturn in 1848 by Mr.

La.s.sell; the two satellites of Mars by Prof. Asaph Hall in 1877; and the discovery of the so-called ca.n.a.ls of Mars by Schiaparelli in 1877. But the purpose of this work is to deal with material inventions rather than scientific discoveries, and the leading invention in optics is the telescope.

Who invented the telescope is a question that cannot now be answered.

For many years Galileo was credited in popular estimation with having made this invention in 1609. But it is now known that, while he built telescopes, and discovered the mountains of the moon, the spots on the sun's disk, the crescent phases of Venus, the four satellites of Jupiter, the rings of Saturn, and made the first important astronomical observations, the invention of the telescope, as an instrument, could not be rightly claimed for him. Borelli credits it to Jansen & Lippersheim, spectacle makers, of Middelburg, Holland, about 1590; Descartes credits it to James Metius; Humboldt says Hans Lippershey (or Laprey), a native of Wesel and a spectacle maker of Middelburg in 1608, naming also Jacob Adriansz, sometimes called Metius and also Zacharias Jansen.

The great impetus given to the study of astronomy by Galileo, in 1609, was followed up by Huygens in 1655 with his improvement, by Gregory's reflecting telescope of 1663, and Newton's in 1668. In 1733 Chester More Hall invented the achromatic object gla.s.s of crown and flint gla.s.s. In 1758 John Dolland reinvented and introduced the same in the manufacture of telescopes. In 1779 Herschel built his reflecting telescope, and in March, 1781, he discovered the planet Ura.n.u.s. In 1789 he built his great reflector. It was while the latter telescope was exploring the heavens that the Nineteenth Century began, and in the early part of this century Herschel laid before the Royal Society a catalogue of many thousand nebulae and cl.u.s.ters of stars. Among the great telescopes of the Nineteenth Century may be mentioned that made in London in 1802 for the observatory of Madrid, which cost 11,000; the great reflecting telescope of the Earl of Rosse, erected at Parsonstown, in Ireland, in 1842-45. This was 6 feet diameter, 54 feet focal length, and cost over 20,000; the magnificent equatorial telescopes set up at the National Observatories at Greenwich and Paris in 1860; Foucault's reflecting telescope at Paris, 1862, whose mirror was 31 inches diameter, and focal length 17 feet; Mr. R. S. Newall's telescope, set up at Gateshead by Cookes, of York, in 1870; object gla.s.s, 25 inches, tube, 30 feet; Mr.

A. Ainslie Common's reflecting telescope, Ealing, Middles.e.x, 1879, mirror, 37 inches diameter, tube, 20 feet; the telescope at the United States Observatory, at Washington, 1873, object gla.s.s, 26 inches, tube, 33 feet long; and the large refracting telescope by Howard Grubb, at Dublin, for Vienna, 1881.

[Ill.u.s.tration: FIG. 194.--TELESCOPE AT LICK OBSERVATORY.]

In more recent times the great refracting telescope by Alvan Clark & Sons, for the Lick Observatory on Mount Hamilton, California, in 1888, attracted attention as superior to anything in existence up to that time. This is shown in Fig. 194. The supporting column and base are of iron, weighing twenty-five tons. This rests on a masonry foundation, which forms the tomb of James Lick, its founder. The tube is 52 feet long, 4 feet diameter in the middle, tapering to a little over 3 feet at the ends. The object gla.s.s is 36 inches in diameter, and weighs, with its cell, 530 lbs. The steel dome is 75 feet 4 inches in diameter, and the weight of its moving parts is 100 tons. This instrument was perfectly equipped with all gauges, scales, photographic and spectroscope accessories, and fulfilled the condition imposed in the trust deed of James Lick, of being "superior to and more powerful than any telescope made." It is a giant among instruments of precision, and its ponderous aspect still a.s.serts the dignity of its purpose, and impresses even the frivolous visitor with a silent and thoughtful respect.

It is not to be understood, however, that the great Lick telescope still maintains its supremacy. The Yerkes telescope, which was exhibited at the World's Fair Exposition in 1893, at Chicago, had an object gla.s.s of 3.28 feet in diameter and a focal distance of 65 feet, and it moved around a central axis in a vast cupola or dome 78 feet in diameter. The Grand Equatorial of Gruenewald, at the recent Berlin Exposition, was even still larger, since its object gla.s.s was 3 feet 7 inches, or nearly 2 inches larger than the Yerkes.

[Ill.u.s.tration: FIG. 195.--GREAT TELESCOPE, PARIS EXPOSITION. 1900.]

Even these great instruments have now been excelled in the Grande Lunette, of the Paris Exposition, in 1900. When it is remembered that an increase in the diameter of any circular body causes, for every additional inch, a vastly disproportionate increase in the cross-sectional area and weight, it will readily be seen how handicapped the instrument maker is in any increase in the power of such a telescope. An increased diameter of a few inches in the gla.s.s lens means an enormous increase in the cross section, its weight and the difficulties attending its successful casting free from imperfections, and the perfect grinding and polishing of the lens. An increased length of the tubular case of the telescope is liable to involve, from the great weight, a slight bending or springing out of axial alignment when supported near the middle for equatorial adjustment, and a few feet increase in the diameter of the ma.s.sive and movable steel dome add greatly to the weight and incidental difficulties of constructing and delicately adjusting it. The great Lunette, see Fig. 195, changes entirely the method of manipulating the telescope, and also, in a measure, its principle of action, so as to avoid some of these difficulties. Its tube, instead of being pointed upwardly through the slot of a movable dome, and made adjustable with the dome, is laid down horizontally on a stationary base of supporting pillars, and an adjustable reflecting mirror and regulating mechanism, called a "siderostat," is arranged at one end, to catch the view of the star, or moon, and reflect it into the great tube, and through its lenses on to the screen at the other end. The tube is 197 feet long, and the object gla.s.s or lens is a fraction over 4 feet in diameter. There are two of these, which together cost $120,000. The siderostat is supported on a large cast iron frame, and is provided with clockwork and devices for causing the mirror to follow the movement of the celestial object which is being viewed. The entire weight of the siderostat and base is 99,000 pounds, the movable part weighs 33,000 pounds, and the mirror and its cell weigh 14,740. The mirror itself is of gla.s.s, weighs 7,920 pounds, is 6.56 feet in diameter, and 10.63 inches thick. To facilitate the free and sensitive adjustment of this great mirror its base floats in a reservoir of mercury. The entire cost of the instrument is said to be over 2,000,000 francs. With the wonderful strides of improvement in all fields of invention, it is not unreasonable to suppose that the revelations in astronomy may keep pace with those of mundane interest, and that great discoveries may be made in the near future. The average individual does not bother himself much about the calculation of eclipses, or the laws which govern the movements of an erratic comet. He is, however, intensely personal and neighborly, and what he wants to know is, Is Mars inhabited? and if so, are its denizens men, and may we communicate with them? The wonderful regularity of the so-called ca.n.a.ls, of apparently intelligent design, already discovered on the surface of Mars, has stimulated this neighborly curiosity into an expectant interest, and who knows what marvelous introductions the modern telescope may bring about?

[Ill.u.s.tration: FIG. 196.--PROF. ABBE'S STEREO-BINOCULAR.]

Many minor improvements have been made in recent years in the form of the telescope known as field and opera gla.s.ses. Probably the most important of these is the Stereo-Binocular, invented by Prof. Abbe, of Germany, and patented by him in that country in 1893, and also in the United States, June 22, 1897, No. 584,976. This gives a much increased field, and also an increased stereoscopic effect, or conception of relative distance, by having the object gla.s.ses wider apart than the eyes of the observer. The field is also flatter, the instrument rendered very much smaller and more compact, and no change of focus is required for changing from near-by to remote objects. The rays of light, see Fig.

196, enter the object gla.s.ses, strike a double reflecting prism, and are first thrown away from the observer, and then striking another double reflecting prism, arranged after Porro's method, are returned to the observer in line with the eye-piece.

[Ill.u.s.tration: FIG. 197.--MODERN MICROSCOPE.]

_The Microscope._--Just as the telescope reveals the infinity of the great world above and around us, so does the microscope reveal the infinity of the little world around, about, and within us. Its origin, like the telescope, is hidden in the dim distance of the past, but it is believed to antedate the telescope. Probably the dewdrop on a leaf const.i.tuted the first microscope. The magnifying power of gla.s.s b.a.l.l.s was known to the Chinese, j.a.panese, a.s.syrians and Egyptians, and a lens made of rock crystal was found among the ruins of Ninevah. The microscope is either single or compound. In the single the object is viewed directly. In the compound two or more lenses are so arranged that the image formed by one is magnified by the others, and viewed as if it were the object itself. The single microscope cannot be claimed by any inventor. The double or compound microscope was invented by Farncelli in 1624, and it was in that century that the first important applications were made for scientific investigation. Most of the investigations were made, however, by the single microscope, and the names of Borelli, Malpighi, Lieberkuhn, Hooke, Leeuwenhoek, Swammerden, Lyonnet, Hewson and Ellis were conspicuous as the fathers of microscopy. For more than two hundred and fifty years the microscope has lent its magnifying aid to the eye, and step by step it has been gradually improved. Joseph J.

Lister's aplanatic foci and compound objective, in 1829, was a notable improvement in the first part of the century, and this has been followed up by contributions from various inventors, until the modern compound microscope, Fig. 197, is a triumph of the optician's art, and an instrument of wonderful accuracy and power. Its greatest work belongs to the Nineteenth Century.