1911 Encyclopædia Britannica/Röntgen, David

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RÖNTGEN, DAVID, sometimes called David de Lunéville (1743–1807), German cabinet-maker, eldest son of Abraham Röntgen, was born at Herrenhag. In 1753 his father migrated to the Moravian settlement at Neuwied, near Coblenz, where he established a furniture factory. He learned his trade in his father's workshop, and succeeded to the paternal business in 1772, when he entered into some kind of partnership with the clock-maker Kintzing. At that time the name of the firm appears already to have been well known, at all events in France; but it is a curious circumstance that although he is always reckoned as one of the little band of foreign cabinetmakers and workers in marquetry who, like Oeben and Riesener, achieved distinction in France during the superb floraison of the Louis Seize style, he never ceased to live at Neuwied, where apparently the whole of his furniture was made, and merely had a shop, or show-room, in Paris. We have, as it happens, a record of his first appearance there. The engraver Wille enters in his journal of August 30, 1774, that “ M. Röntgen, célèbre ébéniste, établi à Nieuwied, près de Coblenz, m'est venu voir, en m'apportant une lettre de recommendation de M. Zick, peintre à Coblenz . . . Comme M. Röntgen connaissait personne à Paris, je lui fus utile en lui enseignant quelques sculpteurs et dessinateurs dont il avait besoin.” Röntgen was first and foremost an astute man of business, and it is not improbable that the moving cause of this opening up of relations with Paris was the accession to the throne of Marie Antoinette, whose Teutonic sympathies were only too well known. Before very long she appointed him her ébéniste-méchanicien. He appears, indeed, to have acquired considerable favour with the queen, for on several occasions she took advantage of his journeys through Europe to charge him with the delivery of presents and of dolls dressed in the Paris fashions of the moment—they were intended to serve as patterns for the dressmakers—to her mother and her sisters. He appears at once to have opened a shop in Paris, but despite, and perhaps because of, the favour in which he was held at court, all was not plain sailing. The powerful trade corporation of the maîtres-ébénistes disputed his right to sell in Paris furniture of foreign manufacture, and in 1780 he found that the most satisfactory way out of the difficulty was to get himself admitted a member of the corporation to which all his great rivals belonged. By this time he had attracted a good deal of attention by the introduction of a new style of marquetry, in which light and shade, instead of being represented as hitherto by burning, smoking or engraving the materials, were indicated by small pieces of wood so arranged as to create the impression of pietra dura. We have seen that Röntgen had been appointed ébéniste-méchanicien to Marie Antoinette, and the appointment is explained by his fondness for and proficiency in constructing furniture in which mechanical devices played a great part. The English cabinet-makers of the later eighteenth century often made what was called, with obvious allusion to its character, “ harlequin furniture,” especially little dressing-tables and washstands which converted into something else or held their essentials in concealment until a spring was touched. David was a past master in this kind of work, and unquestionably much of the otherwise inexplicable reputation he enjoyed among contemporaries who were head and shoulders above him is explained by his mechanical genius. The extent of his fame in this direction is sufficiently indicated by the fact that Goethe mentions him in Wilhelm Meister. He compares the box inhabited by the fairy during her travels with her mortal lover to one of Röntgen's desks, in which “ at a pull a multitude of springs and latches are set in motion.” For a desk of this kind Louis XVI. paid him 80,000 livres. Outwardly it was in the form of a commode, its marquetry panels symbolizing the liberal arts. A personification of sculpture was in the act of engraving the name of Marie Antoinette upon a column to which Minerva was hanging her portrait. Above a riot of architectural orders was a musical clock (the work of the partner Kintzing), surmounted by a cupola representing Parnassus. The interior of this monumental effort, 11 ft. high, was a marvel of mechanical precision; it disappeared during the First Empire. Röntgen did not confine his activities to Paris, or even to France. It has been said that he travelled about Europe accompanied by furniture vans, and undoubtedly his aptitude as a commercial traveller was remarkable. He had shops in Berlin and St Petersburg, and himself apparently twice went to Russia. On one of these visits he sold to the Empress Catherine furniture to the value of 20,000 roubles to which she added a personal present of 5000 roubles and a gold snuff-box—in recognition, it would seem, of his readiness and ingenuity in surmounting a secretaire with a clock indicating the date of the Russian naval victory over the Turks at Cheshme, news of which had arrived on the previous evening. This suite of furniture is believed still to be in the Palace of the Hermitage, the hiding-place of so much remarkable and forgotten art. To the protection of the queen of France and the empress of Russia David added that of the king of Prussia, Frederick William II., who in 1792 made him a Commerzienrath and commercial agent for the Lower Rhine district. The French Revolution and the Napoleonic Wars which so speedily followed, eclipsed Röntgen's star as they eclipsed those of so many other great cabinet-makers of the period. In 1793 the Revolutionary government, regarding him as an émigré, seized the contents of his show-rooms and his personal belongings, and after that date he appears neither to have done business in Paris nor to have visited it. Five years later the invasion of Neuwied led to the closing of his workshops; prosperity never returned, and he died half ruined at Wiesbaden on the 12th of February 1807.

Rontgen was not a great cabinet-maker. His forms were often clumsy, ungraceful and commonplace; his furniture lacked the artistry of the French and the English cabinet-makers of the great period which came to an end about 1790. His bronzes were poor in design and coarse in execution—his work, in short, is tainted by commercialism. As a marqueteur, however, he holds a position of high distinction. His marquetry is bolder and more vigorous than that of Riesener, who in other respects soared far above him. As an adroit deviser of mechanism he fully earned a reputation which former generations rated more highly than the modern critic, with his facilities for comparison, is prepared to accept. On the mechanical side he produced, with the help of Kintzing, many long-cased and other clocks with ingenious indicating and registering apparatus. Röntgen delighted in architectural forms, and his marquetry more often than not represents those scenes from classical mythology which were the dear delight of the 18th century. He is well represented at South Kensington.

RÖNTGEN. WILHELM KONRAD (1845–). German physicist, was born at Lennep on the 27th of March 1845. He received his early education in Holland, and then went to study at Zurich, where he took his doctor's degree in 1869. He then became assistant to Kundt at Würzburg and afterwards at Strassburg, becoming privat-dosent at the latter university in 1874. Next year he was appointed professor of mathematics and physics at the Agricultural Academy of Hohenheim, and in 1876 he returned to Strassburg as extraordinary professor. In 1879 he was chosen ordinary professor of physics and director of the Physical Institute at Giessen, whence in 1885 he removed in the same capacity to Würzburg. It was at the latter place that he made the discovery for which his name is chiefly known, the Röntgen rays. In 1895, while experimenting with a highly exhausted vacuum tube on the conduction of electricity through gases, he noticed that a paper screen covered with barium platinocyanide, which happened to be lying near, became fluorescent under the action of some radiation emitted from the tube, which at the time was enclosed in a box of black cardboard. Further investigation showed that this radiation had the power of passing through various substances which are opaque to ordinary light, and also of affecting a photographic plate. Its behaviour being curious in several respects, particularly in regard to reflection and refraction, doubt arose in his mind whether it was to be looked upon as light or not, and he was led to put forward the hypothesis that it was due to longitudinal vibrations in the ether, not to transverse ones like ordinary light; but in view of the uncertainty existing as to its nature, he called it X-rays. For this discovery he received the Rumford medal of the Royal Society in 1896, jointly with Philip Lenard, who had already shown, as also had Hertz, that a portion of the cathode rays could pass through a thin film of a metal such as aluminum. Röntgen also conducted researches in various other branches of physics, including elasticity, capillarity, the conduction of heat in crystals, the absorption of heat-rays by different gases, piezo-electricity, the electromagnetic rotation of polarized light, &c.

RÖNTGEN RAYS. W. K. Rontgen discovered in 1895 (Wied. Ann. 64, p. 1) that when the electric discharge passes through a tube exhausted so that the glass of the tube is brightly phosphorescent, phosphorescent substances such as potassium platinocyanide became luminous when brought near to the tube. He found that if a thick piece of metal, a coin for example, were placed between the tube and a plate covered with the phosphorescent substance a sharp shadow of the metal was cast upon the plate; pieces of wood or thin plates of aluminium cast, however, only partial shadows, thus showing that the agent which produced the phosphorescence could traverse with considerable freedom bodies opaque to ordinary light. He found that as a general rule the greater the density of the substance the greater its opacity to this agent. Thus while this effect could pass through the flesh it was stopped by the bones, so that if the hand were held between the discharge tube and a phosphorescent screen the outline of the bones was distinctly visible as a shadow cast upon the screen, or if a purse containing coins were placed between the tube and the screen the purse itself cast but little shadow while the coins cast a very dark one. Rtintgen showed that the cause of the phosphorescence, now called Rontgen rays, is propagated in straight lines starting from places where the cathode rays strike against a solid obstacle, and the direction of propagation is not bent when the rays pass from one medium to another, i.e, there is no refraction of the rays. These rays, unlike cathode rays or Canalslrahlen, are not deflected by magnetic force; Riintgen could not detect any deflection with the strongest magnets at his disposal, and later experiments made with stronger magnetic fields have failed to reveal any effect of the magnet on the rays. The rays affect a photographic plate as well as a phosphorescent screen, and shadow photographs can be readily taken. The time of exposure required depends upon the intensity of the rays, and this depends upon the state of the tube, and the electric current going through it, as well as upon the substances traversed by the rays on their journey to the photographic plate. In some cases an exposure of a few seconds is sufficient, in others hours may be required. The rays coming from different discharge tubes have very different powers of penetration. If the pressure in the tube is fairly high, so that the potential difference between its electrodes is small, and the velocity of the cathode rays in consequence small, the Rontgen rays coming from the tube will be very easily absorbed; such rays are called " soft rays." If the exhaustion of the tube is carried further, so that there is a considerable increase in the potential differences between the cathode and the anode in the tube and therefore in the velocity of the cathode rays, the Rontgen rays have much greater penetrating power and are called " hard rays." With a highly exhausted tube and a powerful induction coil it is possible to get appreciable effects from rays which have passed through sheets of brass or iron several millimetres thick. The penetrating power of the rays thus varies with the pressure in the tube; as this pressure gradually diminishes when the discharge is kept running through the tube, the type of Rontgen ray coming from the tube is continually changing. The lowering of pressure due to the current through the tube finally leads to such a high degree of exhaustion that the discharge has great difficulty in passing, and the emission of the rays becomes very irregular. Heating the walls of the tube causes some gas to come off the sides, and by thus increasing the pressure creates a temporary improvement. A thin-walled platinum tube is sometimes fused on to the discharge tube to remedy this defect; red-hot platinum allows hydrogen to pass through it, so that if the platinum tube is heated, hydrogen from the flame will pass into the discharge tube and increase the pressure. In this way hydrogen may be introduced into the tube when the pressure gets too low. When liquid air is available the pressure in the tube may be kept constant by fusing on to the discharge tube a tube containing charcoal; this dips into a vessel containing liquid air, and the charcoal is saturated with air at the pressure which it is desired to maintain in the tube. Not only do bulbs emit different types of rays at different times, but the same bulb emits at the same time rays of different kinds. The property by which it is most convenient to identify a ray .is the absorption it suffers when it passes through a given thickness of aluminium or tin-foil. Experiments made by McClelland and Sir J. J. Thomson on the absorption of the rays produced by sheets of tin-foil showed that the absorption by the first sheets of tin-foil traversed by the rays was much greater than that by the same number of sheets when the rays had already passed through several sheets of the foil. The effect is just what would occur if some of the rays were much more readily absorbed by the tin-foil than others, for the first few layers would stop all the easily absorb able rays while the ones left would be those that were but little absorbed by tin-foil.