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Achievements Of The 19th Century:
 A Century Of Achievement

 Transportation

 Communication

 Engineering

 Marvelous Machinery

 Light And Heat Including Photography

 Electricity

 Mining And Metallurgy

 Agriculture

 Chemistry

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Light And Heat Including Photography

( Originally Published Early 1900's )

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The Nineteenth Century has witnessed a marvelous revolution in methods of producing and utilizing light and heat. The rude processes in vogue at the end of the last Century were almost exactly the same as had been in use for the preceding two or three thousand years, and they were at that but slight improvement on the customs of savage and barbarous nations.

The history of fire as a light giver is both picturesque and interesting. It is thought to have been first utilized in volcanic districts, where sticks of wood can sometimes be ignited by thrusting them into subterranean cavities. The theory has also been advanced that primitive man came into its possession through the agency of the electric storm, when trees might have been set on fire by lightning strokes. Or, as it is known that trees are some-times fired by friction of dry branches, it is not impossible that prehistoric man became acquainted with the fierce element in that way. But by whatever means he did become familiar with fire and it may have been any or all of these phenomena the astute savage recognized its usefulness and the necessity for its preservation, and, at a presumably later age, discovered that he could produce it himself by friction.

This primitive custom, descending to civilized peoples, in time evolved into the more convenient flint and steel process, which probably did not originate until after iron was made. Thus the method of fire-getting by the rubbing of one substance on another continued in use from the days of prehistoric man, through all the ages of barbarism and civilization until early in the present Century, with practically no improvement in all that period.

And then a great discovery was made. In April, 1827, John Walker, a chemist and druggist of Stockton-on-Tees, invented a fire-getting implement which consisted of a splint of wood tipped with a solution of chlorate of potash, sulphur, starch and gum, which ignited by friction on sandpaper or glass, and to which he gave the name of congreve, in honor of Sir William Congreve, inventor of the rocket. Thus the English druggist solved the problem that had baffled the ingenuity of science for more than one hundred and fifty years. The alchemists of the Seventeenth Century had not been unacquainted with the properties of phosphorus, which was discovered by Brand in 1673. He and his contemporaries experimented with the new fire-producing chemical in the hope of substituting it for the old flint and steel sorcery, one of their processes being to rub a bit of it between two sections of coarse paper and allowing the spark of fire to fall upon a "spunk." But the method was inconvenient and impracticable, and, as the use of phosphorus entailed considerable danger, it soon fell into disuse, and the old-fashioned flint and steel process was resumed. Another chemical discovery at the beginning of the present Century gave further impetus to such an invention and ultimately led to the match as we know it to-day. The chemist Berthollet accidently discovered what he termed the "principle of the oxidation of combustible bodies by chlorates in the presence of strong acids." Chancel, in 1805, made practical application of Berthollet's discovery and produced his so-called "oxymariate" matches. These consisted of strips of wood dipped in a mixture of chlorate of potash, sugar and gum, and were ignited by contact with sulphuric acid. As early as 1780 there had been in use an "electro-pneumatic fire producer," in which a jet of hydrogen was lighted by an electric spark. The Dobereiner "platinum lamp" came into existence in 1823. In this hydrogen gas was ignited by contact with spongy platinum. During the use of the platinum lamp there had also appeared in-parts of Prussia a device consisting of a small glass tube, containing equal parts of phosphorus and sulphur carefully mixed together. Splints of wood were thrust into this, and the friction caused ignition.

John Walker's invention, modeled after the idea advanced by Berthollet, was, however, the real precursor of our present day match, and even that had to be greatly improved upon before it was rendered practical or satisfactory. The Walker match contained no phosphorus, the absence of which was responsible for its not being a success commercially. In 1833 wooden friction matches containing phosphorus were manufactured in Vienna, Darmstadt and other European cities, and the use of the new implement spread rapidly. On October 24, 1836, A. D. Phillips, of Springfield, Mass., took out the first patent in the United States for a phosphorus match, the igniting composition being a mixture of sulphur. By this time the people commenced to gain sufficient confidence in the innovation to throw away their ill-smelling and clumsy old tinder boxes, and matches came into use all over the civilized world. A warm discussion on the dangers attendant on the use of phosphorus in match making took place between the years 1840 and 1865. It was claimed that the matches in use were not only dangerous by reason of their being rankly poisonous and highly inflammable, but the workmen employed in their manufacture were subject to a peculiar disease of the jawbone, which was loathsome and eventually fatal. This outcry, which was raised all over Europe and America, gave inventors an incentive to discover processes and compositions that would reduce this danger to a minimum, if not wholly remove it. Lundstrom, of Jonkoping, Sweden, invented the first safety match in 1855. His process consisted in putting the oxiding mixture on the splint and what is known as red phosphorus (a safe form of that chemical) on the box. The new match was a great improvement on the original, and led to the discovery of other non-dangerous igniting mixtures. The use of the safety match was enforced by law in various countries of Europe, and to this day the use of Swedish safety matches only is allowed in Denmark and Switzerland. In late years, however, by the enforcement of regulations regarding ventilation, cleanliness, and the impregnation of the air of the factory with turpentine fumes, match-making has been relieved of almost every element of danger to its workers, and the match itself is quite as harmless as its cumbrous predecessor.

Rivaling in importance the improvement in the process of fire-producing, are the advances that have been made in the methods for its utilization for illuminating purposes. From a tallow candle to an arc light is a far cry, and yet less than a Century ago even the common oil lamp as we know it to-day was unheard of. The nearest approach' to the modern kerosene lamp was a rudely constructed vessel filled with melted animal oil and enclosed in a glass case, and which was really the original prototype of our modern lantern. What was called a lamp consisted of a small earthenware cup and contained melted animal fat or vegetable oil into which a wick was introduced. The wealth and nobility of the world had no better means of illumination than had the simplest laborer. The gold and silver vessels in the palace were the exact counterparts of the crude clay lamps in the peasant's cottage. For out-of-door lights torches were used almost exclusively in the cities, and their mode of preparation differed very little from that employed in the middle ages. They were made of the twigs of resinous woods tied together in a bundle and mounted on a tall sapling or post. For all practical purposes the tallow candle and the more elegant wax taper stood paramount at the beginning of the present Century. It is almost impossible to realize that we have been using lamp chimneys not quite one hundred years, and that the Argand burner, although invented late in the last Century, was not sufficiently improved and cheapened to come into general use until 1830. While not so glorious as the discovery of electric light and of coal gas, the invention of the Argand burner and the subsequent application of the glass chimney as a means of supplying a regular current of air to the flame, marked a distinct epoch in civilization.

So perfect has the common oil lamp now become that with the use of the cheap mineral oils, its light in many instances rivals that of the gas jet or the incandescent lamp. And yet these very mineral oils, almost as plentiful as water to the present generation, were practically unknown to the people of the last Century.

Next in importance to the improvement of the oil lamp as a means of illumination was the discovery and introduction of coal-gas, which belongs almost exclusively to the category of Nineteenth Century achievements. Although his first experiment took place in 1792, it was not until 1802, on the occasion of the celebration of the Peace of Amiens, that Murdock, a Redmuth engineer, made a public display of his process of utilizing the gaseous products of coal for illumination. Though Murdock was the first to put gas to a practical use, he was not its original discoverer. So far as can be learned, that distinction belongs to a Dr. Clayton, who, about a hundred years before, had conceived the idea of heating coal in such a manner as to force out and retain its gaseous constituents. He left an interesting description of his experiment, which he evidently considered more in the nature of a huge joke than anything else. He tells us how he first obtained steam, then black oil, and at last a "spirit" spirit being the name used by our forefathers in the discription of any gaseous substance. Dr. Clayton, according to his chroniclers, utilized his discovery as a means of entertainment for a select coterie of friends, to whom the sudden ignition of the "spirit" when touched with light, caused immense amusement.

And so it remained until Murdock's time a chemical wonder a mysterious and evil-smelling "spirit." In 1807 a few gas lamps were placed in the streets of Lon-don, but not until 1813 did its use become at all general. In that year Westminster Bridge was illuminated with it, and then it came rapidly into use, not only for lighting private houses but for dwellings and public buildings. Like all innovations, it met with fierce opposition in every direction. Even so great and good a philosopher as Sir Humphrey Davy was exceedingly derisive in his expression of opinion regarding the new illuminant. At first he went to the length of declaring that it was absolutely impossible to light London with gas little dreaming that he was at that very time perfecting a system of lighting infinitely more dangerous to time-honored fallacies than was the objectionable and newfangled gas. America welcomed the innovation in much the same spirit as did Humphrey Davy. Philadelphia fought for more than twenty years against its introduction as a means for lighting the city. Peale, in his museum in the State House, had as early as 1816 or 1817 produced a fine illumination through the use of gas obtained from a private plant belonging to a man on Lombard Street, whose dwelling was probably the first in America to be lighted with gas. Peale was immediately enjoined from continuing his luminous exhibition, as it was declared to be a menace not only to the historic old State House, but to the entire city as well. It seemed almost impossible to overcome the general prejudice which resisted every attempt to establish a first-class plant in Philadelphia; this was also true of cities all over the country.

The United States Gazette declared it a folly and a nuisance, and insisted that common lamps would "take the shine off all the gas lights that ever exhaled their intolerable stench." All manner of objections were brought against the obnoxious fluid. The newspapers dwelt emphatically on the dire warning that the introduction of gas would result in terrific carnage and destruction, and that the refuse of the works would kill the fish in adjacent streams. Even from the University of Pennslyvania came the voice of Professor Hare, pro-testing that even if gas were the good thing which its supporters declared it to be, tallow candles and common oil lamps were good enough for him. On March 23, 1833, a formal petition of remonstrance, signed by twelve hundred of the wealthiest citizens of Philadelphia, was carried to the State House. The contention waxed so hot that a special commissioner in the person of Samuel V. Merrick was sent by the council to London and Paris for the purpose of investigating the lighting facilities of those cities. Upon favorable reports from the commissioner, the Council, with much misgiving, reluctantly granted the long-fought-for ordinance. After the victory in Philadelphia, the use of gas spread rapidly all over the country, with the result that now every great coal region has its corresponding area of coke ovens, or gas retorts. These retorts are huge cast-iron vessels, covered with brick masonry, beneath which a large furnace burns continuously. The various volatile constituents of the coal are distilled in such manner as to allow the gas to escape into a reservoir, where it is purified and made fit for use.

The discovery of oil pools of fabulous contents in America not only had a great influence in bringing about better illumination for the great middle class, but it introduced a new kind of fuel, which, for a time, appeared to be inexhaustible. The same territory which produces pretroleum also abounds in greater or less deposits of natural gas, which for a number of years now has served the purpose of fuel to a large part of the population of the United States.

But the use of gas for heating purposes is not restricted to the radius of territory fortunate enough to produce the natural element. The manufactured product is fast taking the place of coal all over the country, for cooking purposes at least. It has been proved to be the best and often the most economical cooking power in existence, as there is no waste to it as with coal. With the development of improved and inexpensive processes for the manufacture of gas, who shall say that the day may not come when the coal fire will have entirely disappeared? Who knows but that a few generations hence the use of the begriming mineral as a fuel in its natural state will be as archaic as would be to us the use of the flint and steel?

The story of the discovery of acetylene gas might be called one of the romances of science. The new illuminant had been known to chemists for years, but the difficulty of its manufacture prevented them from using it. In 1895 T. L. Wilson, of North Carolina, while superintending the production of aluminum by the electric smelting process, noticed a by-product of the operation, the nature and character of which was unknown to him. Upon throwing the substance into a bucket of water a gas was given off, whose chief characteristic seemed to be its penetrating and disagreeable odor. On applying a light Mr. Wilson discovered that the gas burned freely with a luminous flame. A repetition of the experiment proved the unknown substance to be calcic carbide. It was found that a pound of this calcic carbide would yield 5.3 cubic feet of acetylene gas, and a company was formed to manufacture the gas on a large scale. From an economic point of view this gas is of great value, for it can be generated in a house as needed, by a very simple apparatus. Perhaps the most remarkable quality of the gas is the fact that it can be liquified by pressure and put in cans that can be tapped when the gas is needed. A very simple device has been arranged by which the pressure of the gas can be regulated while changing from its liquified condition, and then pass into the various pipes. Acetylene is a most powerful illuminant. It is dazzling in the brightness and steadfastness of its flame, and for this reason is much used in the illumination of bicycles and carriages. It has been conjectured that it may in time supplant coal gas in the illumination of streets, thereby doing away with gas piping, for it is said that lamps can be made in such manner as to generate the gas on the spot. It has been proved that the acetylene can be manufactured at one-third the present cost of coal gas, and in view of this fact it is entirely possible that if the discovery proves as practical as claimed, it will revolutionize the manufacture of gas.

We have already observed Sir Humphrey Davy's attitude in regard to the projected illumination of London by gas-light, and in consideration of the discouragement which he lent that scheme there is a prophetic significance in the fact that in the very first year of the Century he should himself have made an experiment that resulted in the discovery of the electric light as we know it to-day. The electric spark had been familiar to the earlier experimenters with electricity, but not much more familiar than it had been to the ancient philosophers. But it remained for the magic of the Cornish philosopher to seize the evanescent spark and make it burn into a brilliant glow by passing it between two points of carbon. The instrument used by Davy in this memorable experiment was a voltaic battery of 2,000 elements. On separating the two carbon points a very small distance, he saw that the gap was bridged by a slightly convex flame which remained until the distance reached a certain limit, at which limit the arc disappeared and the points quickly became cold. The carbons when slowly brought toward one another did not display any activity or calorific phenomenon, but as soon as they were brought in contact the points became hot, and as soon as separated the arched flame burst forth again. Davy gave this convex flame the name of voltaic arc, and it has been so known ever since. The voltaic arc, however, is not a true flame, there being little combustion; it is rather a nebulous blaze resultant from the incandescence of a jet of particles detached from the electrodes and projected in all directions. The positive carbon has a much higher temperature than the negative, which is scarcely a dark red when the positive carbon at the same distance from the arc is a reddish white over a considerable length. The consumption of the positive electrode for a given time is twice that of the negative. The action of the arc upon the electrodes may be described as that of a trembling blue flame of ovoidal form, into which brilliant particles leap from one carbon to the other, producing a luminous red flame. When the voltaic arc is produced in the air the electrodes diminish rapidly, as both of them burn, but in a vacuum this combustion does not take place. The positive carbon becomes hollow and diminishes in weight and the negative elongates and increases in volume. When the wasting of the carbons widens the arc too much, the current is broken and the light disappears, and to obviate this the modern arc-lamp has an automatic mechanism, the function of which is to feed the carbons forward to the arc as they are gradually consumed and thus maintain the splendor of the illumination.

Arc-lamps constructed on the principle discovered by Davy constitute the most luminous artificial light of the present time. Many ingenious lamps have been invented, all embodying the one original idea. Those devised by Serrin, Siemens, Brockie and Duboscq are probably the best known. Some of them regulate the arc by clock-work and electro-magnetism, and others by thermal effects of the electric current. They are used principally for out-of-door illumination, for large areas, streets, railway stations and lighthouses. In the latter instance the arc is placed exactly in the focus of the condensing lenses of a parabolic mirror, which projects the rays all in any one direction, the beam being visible for thirty miles on clear nights. Specially constructed arc-lights, equivalent to hundreds of thousands of candles, can cast a beam of light a distance of one hundred and fifty miles.

Davy's discovery that a continuous wire or stock of carbon would become white-hot by subjecting it to a current of sufficient strength forms the basis of the modern incandescent electric light. Vacuum incandescent lamps are the only ones which have come into general use. Systems based on the incandescence of carbon or platinum in the open air have been tested, but as yet have not come into practical use. In 1841 De Moleyns patented in England an apparatus for the production of light by the incandescence of platinum wire in a closed glass globe, but the scheme was a failure. In 1845 Starr of Cincinnati invented an incandescent carbon lamp on the same principle, and with the same result. Experiments were also made by De Changy, Lodyguine, Kohn and Swan, with little more success. In 1880 Edison constructed an incandescent lamp that was really satisfactory and of commercial value, and although twenty years have not elapsed since its invention it has reached a state of apparent perfection. The Edison lamp consists of a carbon filament fixed to two platinum wires, a glass bulb in which a vacuum has been formed, and a threaded base inserted in the neck of the bulb and intended to hold the lamp in its socket.

The filament used is a vegetable fiber, to which definite form is given according to its nature, either by means of a die or between cylinders, or by cutting it out while in a plastic mass. The fiber thus obtained is subjected to heating by incandescence until it becomes a dense and resilient carbon. Platinum is used because its properties of expansion and contraction are about the same as those of the glass bulb. The vacuum in the bulb is induced by a mercurial air pump. One end of the filament being inserted in the bulb, the other is connected with the metal screw ferrule at the base of the socket, and when screwed into the socket there Is an automatic connection between the sensitive filament on one end of the screw and the insulated plate at the bottom of the socket. Such is the principle upon which all incandescent lamps are constructed, the only variations being in methods of preparing the filament and of clamping the wires.

From a sanitary and aesthetic standpoint the electric lamp is perfect. Properly shaded it will shed a light that equals the moon-beam for softness; or it can be made to rival the sun in brilliancy. It is pure and healthful, as there is no pollution of the air from combustion. It is not inflammable, and for this reason there is absolute safety from conflagration. It illuminates the street, the home, the office and workshop. It lights our railroad trains, steamships, street cars, carriages and even bicycles. It lights the miner at his toil far down in the bowels of the earth, and it accompanies the diver to the bottom of the ocean. It penetrates the darkness of the seas, throwing a shaft of light many miles in advance, and in war time it turns a powerful searchlight on the operations of the enemy. In the large cities of the country night may be turned into day for all practical purposes. Electric lights are hung high in the air on towers placed at convenient intervals, illuminating immense areas and leaving comparatively few dark spots within the limits of a great city. Indeed the magic of Aladdin's fabled lamp was not more potent that has been the sorcery wrought by the Nineteenth Century wizards when they gave the electric light as a perpetual legacy to an incredulous and marveling world.

But illumination is not the only function of electricity. When the voltaic arc was first discovered, one of its most marked peculiarities was the intense heat which it emitted to the electrodes in action. The chemists, in testing this heat, found that it would melt not only all the metals, but quartz, ruby and even diamond, the hardest substance known. They discovered that the temperature of the opposing carbons was comparable only with the sun, and that they registered 5,000 to 10,000 degrees Fahrenheit, the highest artificial heat known. Sir William Siemens, about the same time that he was constructing his arc-lamp, also invented an electric furnace heated by the voltaic arc. In this furnace Siemens was able to vaporize metallic ores of all kinds. The application of electricity for heating purposes was until recent years confined only to the chemical laboratory, but since electric light has proved to be so great a success, electric heating for all purposes bids fair to soon become fully as important as electric illumination. The electric arc is now applied freely in the iron and steel industries for the welding of boiler plates, wires, rails and indeed all kinds of metal work. It is also used with great success in the heating of railroad trains, carriages and dwelling houses. Cooking by electricity is coming more and more into favor. Kitchen ranges, entirely heated by the electric current, are used in many of the best hotels and fine dwellings of the country. There have also been invented a number of cooking utensils equipped individually with batteries for the generation of the electric current. The principle on which all such articles are based is that of incandescence, the current flowing through a network of fine wires of platinum covered with fire-proof insulating cement in its bottom. The electric radiator is constructed pretty much after the fashion of the steam radiator, which it resembles in appearance, the heat from a strong current being diffused over an area of highly resisting metal. The devices for the utilization of electric heat that have been patented in the past few years are unique and numerous. It is now possible to have bed clothing heated to any degree and a constant temperature maintained, by means of a fine wire network enclosed between the quilts and connecting with an electric current.

The stoves in use at the opening of the Century would be unrecognizable as such at the present day, and as for kitchen ranges, they were unknown and unheard of. The common method of heating an apartment was by the use of the open fireplace, which also served for cooking purposes, except in rare cases. The Franklin stove, invented in 1745, was a great advance over the older forms, but it did not come into general use until the beginning of the Nineteenth Century. It has been described as a rectangular box of cast iron plates, open in front with a sliding shutter, by which the whole might be closed either entirely or partly, for safety or for increasing the draught. The hearth projected in front, and was cast with double ledges to receive the edges of the upright plates, and also with a number of holes, one in the front part for admitting air to the fire from an air flue beneath when the shutter was down; one behind the first upright plate in the back for discharging the air; and three holes near the extreme back edge for discharging the smoke into the flue leading to the chimney. This unsightly monstrosity embodied the principles of the modern air-tight stove, which art and an understanding of hygiene have since combined to make a healthful heating apparatus.

One of the most curious properties of light is its ability to trace images under certain conditions. Like electricity and gas, photography owes its real discovery and virtual development to Nineteenth Century wisdom. The story of photography virtually dates back to the year 1556, when the alchemist Fabricius observed the effect of light upon luna cornea, or horn silver; or chloride of silver as we know it to-day. In its native state horn silver is completely colorless, but so soon as exposed to the light of day it assumes a violet tint. It was not until 1727, however, when a German physician, Johan Heinrich Schultze, of Halle, attempted the taking of copies of some written characters on translucent paper, with very little success. In 1777 Charles William Scheele, a Swede, experimented with the discovery of Fabricius. He discovered that the rays of light are of varied chemical activity. A few years later Senebier made the very important discovery that violet rays of the, spectrum analysis blackened chloride of silver as much in fifteen seconds as red rays did in twenty minutes. In 1801 Ritter of Jena added still further results to these discoveries. Wollaston, the celebrated English chemist, discovered that gum guaiacum, when exposed to blue rays, changed in color, and that those altered portions regained their original tint when exposed to red rays. The French claim that the first photograph was taken by Professor Charles during the course of a lecture delivered by him at the Louvre in 1780, the so-called photograph being a silhouette of one of his pupils. There is, however, n0 authentic report of the Charles experiment.

From the early history of photography it would appear that it was the amusement of all the great philosophers. We find Sir Humphrey Davy dabbling with the science such time as he was not employed in the development of his voltaic arc. In company with Thomas Wedgewood, son of the famous potter, Davy made a number of experiments, the results of which were set forth by him in the Journal of the Royal Institute in 1802. One of the most important of the experiments made by them was what they called sun-drawing, which consisted in placing a solar microscope in the aperture of a camera obscura for the purpose of imprinting on sensitized paper the image produced on the screen. Wedgewood and Davy met with no success in any of these sun-drawing experiments, and it remained for M. Niepce, a French scientist, to continue them with so much success that he is justly entitled to the honor of making the most suggestive developments in connection with the discovery of photography. From 1801 until the end of his life, Niepce devoted himself to his idea of heliography (from helios, the sun). The difficulty encountered by Wedgewood and Davy was obviated by Niepce's discovery that asphalt will become soluble in certain oils. Mixing the asphalt with oil of lavender, he poured the solution over a metal plate, allowing it to dry and form a film. When placed where the image of the camera obscura fell upon it, the result was that the asphalt remained soluble where the shadows had fallen, but became insoluble where the light had struck the film. By several hours exposure in the camera, and a subsequent application of essential oils, Niepce secured a heliograph traced upon the metal plate in lines of asphalt.

The name that is most familiar, however, in the history of early photography is that of Louis Jacques Daguerre, to whom for many years was accorded the chief honor 0f the invention of photography. Daguerre was a painter of opera scenes and the producer of panoramic views, the pictorial effects of which he heightened by an ingenious use of reflected and transmitted light. He became acquainted with the camera obscura in his endeavors to obtain his first sketches from nature. In 1839 his famous spectacular exhibition, Diorama, which was the wonder of Paris, was destroyed by fire, and then the artist devoted himself to the process of photography, which afterwards made him famous. Some years before this accident Daguerre had become a collaborator with Niepce, and until the latter's death, in 1833, they worked together on the heliograph process. The discovery of the daguerreotype was purely accidental. Several plates that had been under-exposed were placed in a dark room in which were various chemicals. The plates were thought to be useless, as no images had appeared. Some time afterwards, in searching for something else, Daguerre discovered the discarded plates, and, to his amazement, there was a picture on each one 0f them. He accounted for the phenomenon only by the fact that the plates must have been exposed to the action of some chemical lying in proximity to the plates. Removing the chemicals one by one, he discovered that the secret of the art was concealed in a vessel of mercury, which evaporates at an ordinary temperature. This incident occurred some years subsequent to Niepce's death, and according to the terms of the agreement he made with Daguerre, his name would also have been attached to the discovery, had it not been that after Niepce's death his son relinquished this right for material considerations.

Thus far photography had only been employed upon metal. Henry Fox-Talbot, after years of faithful experiment, solved the problem of "fixing" a photograph on sensitized paper. In the year 1850, the collodion-film on glass was perfected and came into use as a sensitizing material. This method produced as beautiful a likeness as the daguerreotype itself and at much less cost. Shortly afterward positives were printed from the transparent negatives on properly prepared paper, and thus the process now in use was initiated. There have been end-less modifications and improvements upon the original method, mainly to the end of increasing the sensitiveness of the plates so that quickly moving objects could be photographed with lifelike accuracy.

It has long been the dream of photographers to discover some method by which they could produce photographs in all the colors of nature. Thus far the process has not been perfected, but the developments of the past few years are extremely encouraging. Soon after he had heard of photography, in 1837, Sir John Herschel was led to experiment with the spectrum in the hope of fixing the natural colors of the image. Herschel succeeded only partially, but it was enough to incite the ambition of every photographer and scientist from that time down to the present. Edmund Becquerel, Niepce de St. Victor, Poitevin, St. Florent and Captain Abney ably followed up the research started by Herschel. The method adopted by these early investigators consisted in exposing the properly prepared plate to the light of the spectrum until the different colors were impressed on the negative. But the trouble was that as soon as exposed to the light the colors faded, there being no chemical to fix them permanently. In 1891 Professor Gabriel Lippmann, of Paris, introduced a new process, which was a distinct advance toward the solution of the problem of color photography. The method employed by him is on the principle of "interference" instead of chemical action, and is exemplified in the colors of soap bubbles, mother-of-pearl and other iridescent objects. Professor Lippmann explains it as follows: "The film in which the photograph is taken may be made of any substance, provided it is transparent and grainless. Exposure takes place in contact with a metallic mirror. The effect of the latter, which is formed by running a layer of mercury in behind the film, is to reflect back the incident colored rays, and thus make the incident waves stationary. The stationary vibrations, falling in the interior of the sensitive film, impress their own structure upon it, and by virtue of the structure thus imparted, the brown deposit of silver, when viewed by reflected white light, appears imbued with the same col-ors as are possessed in the image in the camera."

Professor Lippmann declares that the colors produced in this way will be perfectly true if exposure and development are right. Development and fixing are effected in the ordinary manner, and the only drawback to the practicability of the process is that it has thus far resisted all attempts to reproduce prints from the negative.

It would be difficult to name a branch of industry or science which has not been benefited by photography. The applications to which it has been put are quite as marvelous as the art itself. Late in the year 1895 a great sensation was caused throughout the civilized world by the announcement that a German scientist, Professor Röentgen, of Würzburg, had succeeded in photographing the bones of the hand through its covering of flesh by the agency of rays proceeding from a spherical glass tube. The instrument by which the New Photography was first observed is known to scientists as the Crookes' tube, so called from the fact of its first experiment in England being made by Professor Crookes. Some twenty years before Röentgen made his discovery, two German physicians, Hittorf and Goldstein, made some interesting experiments with these tubes, which may be described as glass cylinders from which the air has been exhausted. In each end of the tube is placed a disk, one of which conveys an electric current to the interior of the tube, and the other carries it away, making the return wire to a battery. The generation of light takes place when the proper fluorescence is obtained within the tube, and it is caused by the action of the electric fluid in disturbing the molecules of rarified air. In the experiments made by Hittorf and Goldstein it was observed that the light visible to the eye, passing from one electrode to the other, was due to the imperfection of the vacuum, and that the greater the vacuum became the weaker the light was until it disappeared entirely when a perfect vacuum was rendered. It was further noticed that with the disappearance of the light the tube became fluorescent, which indicated that the fluorescence was caused by the oscillating discharges of invisible rays, and that the cathode was the point of origin.

About a year prior to the Roentgen discovery Lenard, of Bonn, published a report of certain discoveries he had made in "shadowgraphs," as he called them. He proved that it was possible to obtain shadows of objects through practically opaque substances, and to make impressions of these shadows on photographic plates. For some unexplainable reason, however, Lenard's paper attracted very little attention, and was almost forgotten when Roentgen's discovery was announced.

The light generated within the tube is intensely luminous, but it is luminous in an entirely different way from ordinary light. It has the peculiar properties of rendering translucent objects which to us are opaque, and vice versa. Slate, wood, leather and carbon are much more transparent to the X-rays than glass, some varieties of which are entirely opaque to their light. Paper absolutely opaque to the fiercest ordinary light, is so trans-parent when subjected to X-rays that the light will pass through a book of a thousand pages. Flesh and skin are transparent, while bone is opaque ; hence the value of the discovery in surgery.

Numerous theories and suppositions have been extended regarding what the X-rays may in reality be, and to account for their phenomena. Some scientists hold that they are ultra-violet rays of light with vibrations a million times greater than ordinary light; another is that they may be the missing longitudinal waves in the ether. If the latter supposition ever leads to anything tangible it will open up an entirely new department of physics, and may lead to discoveries of which we do not now dare dream.

Scarcely less of a surprise than the X-rays to the world was the development of photography in the form of the Cinematograph, the Kinetoscope, the Theatrograph, etc., etc., all of which might be properly termed "animated photography." The first patentee of this interesting application of the photographers' art was W. FrieseGreene, who invented a camera in 1889 for the rapid taking of consecutive photographic views; combined with the camera was an optical lantern which threw the images of the camera upon a screen, and by means of a handle the successive pictures were moved s0 rapidly as to give the appearance of life. The idea was not exactly new. It had been experimented with before by both Marey and Muybridge, and was known as the zootrope or the wheel-of-life. But FrieseGreene was the first to construct a machine for popular purposes. About the same time that FrieseGreene was taking out his patent Edison came forth with his Kinetoscope, constructed on the same principle. The Kinetoscope was soon followed by the Cinematograph and various other inventions, all embodying the same idea, and designed for the same purpose that of amusement. These apparati have since become so perfected that they can present a moving scene with almost lifelike fidelity.

The application of photography to the printing industry has been of incalculable value to civilization, in that it has had a tendency to materially decrease the price of books and engravings. These applications have been many, but the chief one is the process of photo-block printing, invented by Walter B. Woodbury in 1866, which he followed up a few years later with the stannotype. By these inventions photo-engraving has become one of the fine arts. The system of letter press printing, by which an author's own manuscript may be printed from in his own chirography, is another application of the art of photography which is as marvelous as the Kinetoscope or the X-rays. This process is the invention of Mr. Friese-Greene, and was suggested to him while experimenting with another invention.

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