HEINRICH GEISSLER: PIONEER OF ELECTRICAL SCIENCE AND VACUUM TECHNOLOGY

SCANNING OUR PAST HEINRICH GEISSLER: PIONEER OF ELECTRICAL SCIENCE AND VACUUM TECHNOLOGY T he seemingly unrelated instrumental equipment supporting several of the main discoveries in physics at the beginnings of the socalled Second Scientific Revolution, at the close of the 19th century, usually had elements in common. Three outstanding discoveries are good examples. As part of his studies on the phenomenon of luminescence in his darkened laboratory at the University of Würzburg, in November 1895, the German experimental physicist Wilhelm Konrad Röntgen (1845– 1923) discovered a new and different kind of rays, X-rays, produced by the impact of cathode rays on a material object. Only a few months later, in February and March 1896, the French physicist Antoine-Henri Becquerel (1852–1908) accidentally discovered natural radioactivity as a new form of radiation while investigating a probable relation existing between the fluorescence of some uranium minerals he studied and the recently discovered X-rays. Finally, explorations of the properties of cathode rays, originally focused on the link between ordinary matter and the electrical charges on the atom, were responsible for the ultimate conclusion in 1897 by the British scientist Joseph John Thomson (1856–1940) that atoms of Digital Object Identifier: 10.1109/JPROC.2015.2461271 This article provides an account of Heinrich Geissler’s scientific achievements, placing special emphasis on his early contribution to the development of the cathode ray tube. all substances contain the same kind of negative particles: the electron. Directly, or indirectly, the common element in all these discoveries was the experiment on electrical discharges in gases. The detection of cathode rays was a consequence of the investigation of the discharge of electricity through rarefied gases. This latter phenomenon, which led to the birth of electronics with the invention of the electron vacuum tube in 1909, has been studied since the late 17th century. Many people contributed to this development with experimentation and technological factors. The glass tube invented by Heinrich GeisslerV the Geissler tubeVnot only allowed a clear demonstration of the electrical discharge and contributed to the discovery of the cathode rays, but over the decades also led to a greater or lesser extent to many other pioneering developments in electronics and telecommunications, such as the light and flash bulbs and a number of projection technologies. This article provides an account of Geissler’s scientific achievements in the context of the physics of his time, placing special emphasis on his early contribution to the development of the cathode ray tube. I. FORMATIVE Y EARS Johann Heinrich Wilhelm Geissler (Fig. 1) was born on May 26, 1814, in Ingelshieb, a little village in a forested mountainous region in central Germany. He was the first of 11 children of Johann Georg Jacob Geissler (1786–1856), a self-taught glass bead maker and a manufacturer of instruments such as barometers and thermometers, and Johanna Rosina Eichhorn (1798–1839), a daughter of a glassmaker. The family’s very poor living conditions forced the children to work from the age of five in the only jobs available to a majority of inhabitants of the village: the lamp blown glass and cottage industries. The difficult social conditions of the time forced the Geissler brothers, 0018-9219 Ó 2015 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. 1672 Proceedings of the IEEE | Vol. 103, No. 9, September 2015 Scanning Our Past Fig. 1. Heinrich Geissler. one after another, to leave home in order to look for better lives, some of them, as was the case for Heinrich, in a seemingly predestined professional career as glassblowers [1]–[4]. Geissler began working when he was very young. After having become an apprentice in glassblowing in SaxeMeiningen, a Duchy of Central Germany, he became a Handwerksbursch (journeyman). Under the system that had become common by that time, such a young specialized craftsman would spend a certain number of years traveling either within his own country, or outside its borders, accepting employment wherever it was offered and being paid by the day. His aim would be to become acquainted with the different methods of doing the work, and thereby perfect it and become competent enough to enter the business on his own account. This period, which for Geissler extended to about one decade, included him visiting cities in countries such as Germany, France, and The Netherlands, and concluded in the early 1850s when he settled permanently in Bonn. There, he bought a house that he adapted to the requirements of his workshop, and joined the University of Bonn as a mechanic. Although most of the instruments Geissler produced at Bonn were aimed at the physics community, others served the interests of different professionals such as chemists, medical doctors, physiologists, and mineralogists, who formed part of the long international client list he was able to build up during his career. Names such as Eduard Friedrich Wilhelm Pflüger (1829– 1910), a Professor of Physiology also at the University of Bonn and responsible for the law that bears his name correlating electrical stimulation and muscular contraction, Hermann Vogelsang (1838–1874), the first Professor of Mineralogy and Petrology at the Polytechnic School of Delft and an important figure in these areas during the 19th century, and Justus Freiherr von Liebig (1803–1873), later Baron, a German chemist informally considered to be the founder of organic chemistry, are examples of the names included in this list. Several elements allowed Geissler to closely work with such important scientists. The most relevant were: the renewed reputation of science studies focused on the achievement of practical objectives that characterized those times, the little practice in practical work of most researchers due to the generally sparse opportunities for their physical laboratory training, and the little availability or absolute inexistence of tenured mechanics or instrument makers at many universities. The range of products in Geissler’s workshop included not only all the glass laboratory instruments and apparatuses, then in use, but also some of his own innovations. One example is a vaporimeter he patented [Fig. 2(a)] as a result of a Bonn industrialist’s request, in which the vapor pressure exerted upon a column of mercury gave a measure of the alcohol content in liquid beverages [5]. Another is a pycnometer [Fig. 2(b)], jointly designed with the Russian chemist Dmitri Ivanovich Mendeleev (1834– 1907) in 1859, which, provided with an accurate and delicate thermometer, allowed the determination of the density of liquids and its relation with temperature [6]. The standard thermometers designed by Geissler are better known as the first result of what would later become a successful Fig. 2. Geissler’s instruments. (a) Vaporimeter [8]. (b) Pycnometer [9]. association with the Professor of Mathematics and Physics at the University of Bonn, Julius Plücker (1801–1868). The thermometers differed from those then in use by utilizing a thinner, although still strong, glass by incorporating the concept of capillarity, and by a higher precision resulting from using a new glass balance with a sensitivity of 0.1 mg of mercury for their calibration [7]. By using these ingeniously contrived instruments, in which mercury was made to exactly compensate for the expansion of glass, both men were able to determine the coefficient of cubical expansion of ice of 0.0001585, and to demonstrate that water reached its maximum density at 3.8  C (later determined to be 3.98  C). In 1855, Geissler was rewarded with the Gold Medal at the World Exhibition in Paris due to his excellent work on fine glass and its different applications to science and instruction. II . VACUUM PUMP: THE FIRST OF TWO OUTSTANDING TECHNOLOGICAL DEVELOPMENTS Two of Geissler’s achievements, the development of an improved vacuum pump and its subsequent application Vol. 103, No. 9, September 2015 | Proceedings of the IEEE 1673 Scanning Our Past to the technique for making the tubes that later would bear his name, place Geissler as one of the main pioneers in the study of electric discharges of rarefied gases. The realization that high vacuum levels were essential for studies of electrical discharges led to great advances in physics in the second half of the 19th century; indeed, those advances would be unthinkable without highly developed vacuum technology. This fact had been identified before Geissler’s time. Much earlier, and still far from any possible association with electricity, experimenters like the French astronomer Jean-Felix Picard (1620–1682), for example, had observed strange and intermittent glow discharges in the vacuum space above the mercury surface when a mercury barometer was shaken, and that these discharges were the strongest when mercury moved most vigorously up and down in the tube [10]. The Swiss mathematician Johann Bernoulli (the elder) (1667–1748) generated the first widespread and intensive interest in the phenomenon by suggesting in 1700, while teaching at Groningen, The Netherlands, the interaction of a ‘‘first element’’ squeezed out of mercury and freed to vibrate with the rapidity necessary to produce light with a ‘‘second element,’’ or ‘‘celestial globules,’’ entering through the pores of glass of the barometer, as the real cause of light so produced, or of the mercurial phosphor, as it was then called [11]. Bernoulli also reported that a clean and dry barometer, extremely pure mercury, and minimum contact between air and mercury were essential requirements for producing light, and that the presence of small amounts of air produced a short-lived luminescence in the form of tiny sparks rather than as the continuous flame like light produced in vacuo. Although it is true that a partial vacuum had been created as early as the 3rd century before the Christian era by Hero of Alexandria, the vacuum technology only began to develop in a coherent fashion at the time of Otto von Guericke (1602–1686), a 1674 widely famous German scientist and inventor, by his celebrated experiments in which opposing teams of horses in Magdeburg were unable to separate two evacuated hemispheres. von Guericke, who justly was the man that constructed the earliest mechanical device for generating what later was recognized as electrical charges and produced glow discharges by rubbing a sulphur globe [12], raised significant issues with the ‘‘torricellian void,’’ and, around 1650, developed the first rudimentary air pumpVa sort of syringeVto pump air directly out of a vessel. News of von Guericke’s achievements spread throughout Europe, starting many other interesting experiments. About a decade later, the Anglo-Irish natural philosopher, chemist, and physicist, Robert Boyle (1627–1691), perfected von Guericke’s air pump and allowed experimenters to create a partial vacuum in a glass bell at the top of a device by pumping air out using a handle. Later, in 1709, the English scientist Francis Hauksbee (1660–1713) produced a two-cylinder pump of much better design, which reduced not only the need for human labor, making the experiments a one-man task, but also the pumping time, since no pauses were required between the plunger strokes to operate the stopcocks [13], [14]. The very sophisticated and wellthought-out design included a receiver (the glass vessel for experiments) on a plate on top of the pump structure, and a gearwheel with two racks, each connected to a piston in a cylinder [15]. The new model was arranged in such a way that the pistons were balanced against each other as they were driven in opposite directions by the rack and pinion, being capable of reaching 1.9 mm Hg in 2 min. The considerable time that Hauksbee would devote from then on to the improvement of his air pump and its possible employments, as well as the compliance with the requirements of the Royal Society were the elements that contributed to the nature of his subjects of study and scientific re- Proceedings of the IEEE | Vol. 103, No. 9, September 2015 search projects. His experiments with which a flickering and bluish light was created inside rotatable and previously evacuated glass globes and cylinders after rubbing their outside surface, the comparison of light produced by mercury in a vacuum with that produced under a partial exhaustion of air, and the systematic identification of low air pressure and the motion of mercury against glass as critical factors in the production of light in glass vessels [16] turned him into not only the first person to perform the scientific study on the effects of electrostatics in vacuum, but also made his apparatus the forerunner of discharge lamps of the 19th and 20th centuries [17]. The colorful displays resulting from these and similar experiments carried out by him and other scientists in the following century were more usually regarded as curiosities to be demonstrated in public by the increasing number of amateur investigators in different countries in Europe, and different explanations, such as chemical changes occurring in gas, associated with metallic spectra caused by volatilization and ignition of electrodes [18], for example, were often given at the time as their interpretation. After 1750, the technical improvement of the air pump became a problem mainly in engineering and, with small refinements, Hauksbee’s design remained, in principle, unchanged until the mid-19th century. The small demand from the experimenters for lower pressures and the limitation of the measurable pressures in the mercury manometers to about 0.5 mm Hg contributed to this particular state of things. In the 1740s, the French clergyman and physicist Jean Antoine Nollet (1700–1770), often known as AbbéNollet, conducted experiments in a sealed glass bulb about the size and shape of an ostrich egg, from which the air had been pumped. In the ‘‘electric egg,’’ as he called it, the discharge tube was quite separate from the source of electric charge, but connected to it by a wire. Scanning Our Past The next serious experimental advance in the studies of glow discharges and the spectral emission from the glows came a century and a decade later, and involved Geissler and Plücker. The low demand for lower pressures from experimenters as well as the limitation in the measurable pressure to about 0.5 mm Hg with the available designs of mercury manometers were two reasons for little improvement of the ultimate vacuum in about two centuries. The increasing number of researches on electrical phenomena starting in the 1850s, including discharge tubes, required, however, higher vacuums. Incandescent lamps resulting from attempts at creating a light bulb in those times burned for short periods of time, not only because of the quality of the filaments, but also because of the excessive amount of air inside the bulb. Attempts to introduce mechanically operated valves and reduce the dead space at the bottom of the cylinder proved to be insufficient to solve the problem of leakage at the pump’s pistons and other working difficulties, forcing, since 1850, changes in other directions in order to get operation pressures below 0.01 atmospheres. The problem was solved in 1855 when Geissler designed a mercurial vacuum pump based on moving a column of liquid mercury instead of mechanical pistons, which allowed him to eventually reach absolute pressures of about 0.1 mm Hg. The model was based on a new type designed more than 130 years before Geissler’s time by the Swedish scientist and theosophist Emanuel Swedenborg (1688– 1772), which combined Torricelli’s mercury work of nearly a century earlier with von Guericke’s pump [19]. Swedenborg replaced the solid piston of the mechanical pump by a column of mercury, which by being alternately raised and lowered gradually exhausted a vessel. A little table with three long legs, which carried the glass bell jar that was to be exhausted, was the base unit of the equipment, which was additionally connected at the bottom with an iron vessel, from which the first iron tube descended perpendicularly, which, by its part, joined the second one by a flexible tube of leather. Mercury which filled both tubes was made to rise and fall by placing the moveable tube upright, or laying it down. In this way, the iron vessel, provided with the required valves, was alternatively filled and emptied with liquid metal. Geissler modified Swedenborg’s model by connecting the mercury reservoir to a glass bulb via a flexible rubber tube, the latter being provided with a two-way valve by means of which it could be connected either to the outside air or to the vessel to be exhausted. Lowering the reservoir would draw gas out of the vacuum system and into the bulb, while the immediate closing of the valve would isolate the system and made the reservoir rise again, compressing the trapped gas and pushing it out of the system. Repeatedly lifting and lowering the reservoir led to the required extremely low pressures [20]. Geissler’s work began in 1855 and the pump was presented to the public three years later. It was first described in a pamphlet prepared by W. H. Theodor Meyer (1820-?), the curator of Bonn University’s physics cabinet, during the 1857 meeting of the Society of German Natural Scientists and Physicians (Fig. 3) [21]. While fairly effective and generating better vacuums than those obtained with piston pumps, Geissler’s pump was expensive, difficult to handle, and very slow to operate, requiring a very careful coordination between the turning of the valve and the mercury level [22]. Improvements to Geissler’s pump by two other German instrument makers, proposed in the following decades, partially solved this drawback. In 1862, a German physicist, August Joseph Ignaz Toepler (1836–1912), introduced a modification using the same principle applied by Torricelli in his famous experiment [Fig. 4(a)]. In the simplified pump, which is still in use today, the mercury reservoir and the flexible tube were retained, but the two-way valve was replaced by a T-junction using mercury itself to act as a seal [24]. While the vessel to be exhausted was connected to the torricellian vacuum, the new arrangement of tubes improved the passage of air to be expelled. The other great improvement was made 11 years later, in 1873, when the German-born and naturalized British chemist Hermann Sprengel (1834– 1906) devised a stunningly simple apparatus in which droplets of mercury from a receiver dripped steadily, acted as pistons in a cylinder trapping packets of gas in the discharge glass tube, and carried them away [Fig. 4(b)]. The portion of trapped air became smaller as the process went on, until the mercury flow became continuous and a very good vacuum level was reached [25]. The manual recirculation of mercury introduced in the new model was converted only three years later to a self-recycling apparatus [Fig. 4(c)] by Sprengel’s colleague and compatriot Lambert Heinrich von Babo (1818–1899). The new design could operate with little or no supervision and could achieve lower vacuum than anything else available at the time (about 0.0006 mm Hg). In line with the pattern shown by most vacuum pumps until the 20th century [26], its better degree of vacuum contrasted with its low pumping speed. When 10 kg were lifted up and down by hand and a pump speed of about 0.004 ‘/s was reached, it required approximately 6 h of pumping to evacuate a vessel of 6 ‘ from 0.1 mm Hg to about 2  10 5 mm Hg [27]. Geissler’s pump found one of the first industrial applications, if not the first one, in the researches carried out by Thomas Alva Edison (1847–1931), which led to the development, pilot production, and mass production of carbon-filament incandescent lamps, and to the creation of a practical electric lighting system. From the very earliest attempts to produce a practical incandescent light, it was clear that the glowing element must be in a vacuum in order to prevent oxidation and thus increase the lifetime of the Vol. 103, No. 9, September 2015 | Proceedings of the IEEE 1675 Scanning Our Past Fig. 3. Geissler pump. (a) Original drawing [21]. (b) Schematic illustration of the physical principle [23]. (c) Complete apparatus as it was commercially available [23]. filament. The vacuum of the order of 2.5 mm Hg provided by the only vacuum pump available to Edison in those times, a manual piston type with two cylinders, had proved to be insufficient for the experimental requirements. The alternative of experimenting with relatively inert platinum, which needed protection from melting rather than from oxi- dation, led him to unsatisfactory results. Conscious as Edison was that the use of higher vacuum was an essential requirement, he proceeded to obtain Fig. 4. Improved models of the Geissler pump [23]. (a) Toepler’s pump. (b) Original Sprengel’s pump. (c) Self-recycling Sprengel’s pump. 1676 Proceedings of the IEEE | Vol. 103, No. 9, September 2015 Scanning Our Past Fig. 5. Combination of (A) Geissler’s pump, (B) Sprengel’s pump, and (C) McLeod’s gauge. (a) Laboratory scale [28]. (b) Arrangement in Edison’s pilot plant [30]. all possible information on the subject. The good vacuum achieved with Geissler’s pump in March 1879 was not sufficient, however, because of both the necessity for repeating the process many times and the impossibility of continuous pumping. Edison decided then to try a Sprengel pump, which had the advantage of being able to pump continuously during heating of the carbon filaments that were the next object of study. A combination of both types of pumps, described in a contemporaneous scientific publication, allowed the attainment of vacuums of about 10 6 atmospheres, sufficient to solve most of his technical problems [28]. A Geissler pump for rapid evacuation, a Sprengel pump for continuous pumping, and a McLeodgauge pump (developed in 1874 based on Geissler’s pump) for pressure measurement became the elements of an arrangement that combined all the features required for lamp experiments (Fig. 5). By midAugust 1879, Edison had assembled at least eight different arrangements with both types of pumps, with the collaboration of Ludwig Boehm, a fulltime glassblower who had apprenticed under Geissler. By 1903, five of the U.S. patents bearing Edison’s name were up for improvements and automation of combinations of Geissler’s and Sprengel’s vacuum pumps [29]. Experimenting with carbon as an incandescent substance, which before platinum had failed due to problems with the vacuum, and using the improved vacuum system, Edison was able to produce light, for the first time in October 1879, which burned for 14.5 h with an intensity of 30 candles. I II . DISCHARGE TUBES: THE OTHER OUTSTANDING TECHNOLOGI CAL DEVELOPM ENT Although sporadic, the first quantitative investigations of continuous gas discharges were made in the mid18th century by the Polish scientist Gottfried Heinrich Grummert (1719– 1776), who studied alternatives to illumination in mines where light from fire could not be used because of the danger of explosions. His discovery that an exhausted glass tube did not need to be rubbed to show the electric light but would glow if connected to, or merely brought near, an electrified conductor [31] was followed by other studies carried out by Nollet and the British botanist and physicist William Watson (1715–1787). Nollet generated electric discharges in his exhausted ‘‘electrical eggs,’’ and found that the conduction of electricity through the residual gas in an exhausted glass vessel toward the body of the investigator caused the vessel to become full of light when his hand was brought near it, and to be much brighter when his hand was spread over glass. He explained this and other electrical phenomena on the basis of his illfated theory of affluent and effluent currents of electricity [32], [33]. The collision of particles of the effluent stream with those of the opposite moving affluent stream was responsible for excitation until a state of luminous emission. Watson, for his part, not only showed that the flow of charge through gas in a sealed container increased as pressure was lowered, but also proved, using a Leyden jar, that discharge of static electricity was actually an electric current [34]. One century passed until new relevant developments occurred. Looking for insights into the nature of electricity, the British chemist and Vol. 103, No. 9, September 2015 | Proceedings of the IEEE 1677 Scanning Our Past later physicist Michael Faraday (1791–1867) spent several months in 1838 studying the various forms of discharge of electricity through several rarefied gases, such as hydrogen, nitrogen, air, hydrochloric acid gas, and coal gas. His intention was to confirm the validity of his general view that all electrical phenomena depend on the action of contiguous matter particles [35]. A few years before, studies carried out by the Dutchman Martinus van Marum (1750–1837) showed that spark discharges at atmospheric pressure exhibited different colors according to the gas used [36], and about the same time Charles Wheatstone (1802– 1875) observed that brush discharges at the end of a singly charged conductor were not, as might appear, continuous discharges of the surrounding medium, but a rapid succession of intermittent discharges [37]. Faraday took up Wheatstone’s experiments, being convinced that a comprehensive theory of the flow of electricity should include phenomena associated with the conduction of electricity in gases under different conditions. Experiments carried out at pressures close to 0.04 in of mercury (average atmospheric pressure at sea level is 29.92 in of mercury) showed that as the amount of air in the tube decreased, a faint glow between the electrodes could be seen, but it did not enable him to explore this effect completely because technology was not then advanced enough to produce higher vacuums within the tube. A significant feature was his discovery that the glow in discharge was not continuous, but separated into bright regions close to the electrodes and a dark region in the middle. The existence of the so-called ‘‘Faraday dark space’’ in discharge tubes renewed even more interest in studies on luminous effects due to the conduction of electricity through gases at very low pressures, mainly because of some initial observations of the existence of a relation between the reduction in pressure and the expansion of the dark space and the fading of the color in the electrodes. 1678 Limitations in the voltage source required to carry out the experiments in the beginnings of 1840s were another reason for the lack of interest in studies on the conduction of electricity through gases and the temporary interruption of the researches on gas discharges. The bulky batteries and the complicated and expensive electrostatic generators used until then to supply the high tension for these studies were cumbersome to use, and, most importantly, could not generate a sufficiently high voltage. A solution appeared in the form of the induction coil, first developed in the 1830s. In contrast to the continuous steady current produced by electrochemical batteries, the output of the induction coil, operating on the principle of the transformer, was an interrupted current of much higher potential. The instrument, based on Faraday’s discovery of electromagnetic induction of 1831 and the invention of the electromagnet by William Sturgeon (1783–1850), had its origins in the almost simultaneous, although independent, innovative researches of two men: the Irish priest and scientist Nicholas Joseph Callan (1799–1864) and the American electrical inventor Charles Grafton Page (1812–1868). More than a decade later, in the early 1850s in Paris, the German instrument maker Heinrich Daniel Ruhmkorff (1803–1977) also began making powerful induction coils. Such coils had an inner primary winding of a few heavy turns, and an outer secondary winding of many more fine turns, which could provide very high voltage discharges that produced sparks in open air at five to ten times a second (Fig. 6) [38]. The new apparatus created periodic interruptions of current in the primary coil circuit, which induced stepped up pulses in the secondary coil. The more secondary turns there are, the higher the voltage. Initial difficulties associated with higher frequency required to operate the switch more frequently in order to generated frequent voltage pulses were solved by using the electro- Proceedings of the IEEE | Vol. 103, No. 9, September 2015 Fig. 6. Ruhmkorff induction coil. magnetic force of the coil itself to move the switch. The new apparatus was a much less expensive and more convenient source of high voltage than either an electrostatic generator or a thousand or more battery cells connected in series. It produced a peak potential of many thousands of volts, and the current drawn by the discharge tube was of the order of one milliampere. William Robert Grove (1811– 1896), a lawyer and a professor for a short time at the London Institution, with interests in physical matters, was the first in England to use a Ruhmkorff coil to create an electric discharge through gas at low pressure. Grove, who a few years earlier had an idea of producing light by sealing a conductor in a glass vessel and heating it electrically, and had devoted much time and money to the study of this phenomenon, discovered that the striated patterns observed in the glowing gas accompanied all electric discharges in vacuum tubes [39]. His recently developed vacuum pump and a platinum-to-glass seal he invented enabled Geissler to produce a type of sealed dual-electrode gas filled tubes that glowed when current passed through them, initially aimed at investigating the recently opened field of spectra of different gases (Fig. 7). Geissler’s interest in them was probably influenced by his brother Friedrich, who two years before in Amsterdam had made similar tubes filled with mercury vapor for the Dutch mathematician and physicist Volkert Simon Maarten van der Willigen (1822– 1878). What Geissler had done was attach the two high-potential terminal wires from an induction coil to an equal number of ends of a small and thinwalled glass tube into which he had Scanning Our Past Fig. 7. Geissler tubes. (Credit: courtesy of Dr. Günter Dörfel.) previously sealed short pieces of platinum wire, and then exhausted air from the tube. A green–yellow phosphorescence of low intensity was induced in the glass walls nearest the cathode when electricity was discharged through the tube. The light could only briefly be observed because of the physical difficulty of maintaining low pressure for more than a few moments. When the terminals of the tube were insulated, the shape of light varied. The operating principles for the new object were different and far more complicated than those of the arc and incandescent lamps [40]. Electric current was passed through the tube between the electrodes when pressure inside was very low, regardless of the known fact that gases are commonly good electric insulators. The electric discharge thus produced filled the tube and gave off light. Higher voltages were required when the inner pressure decreased to below a minimum value. Most of the voltage was employed in overcoming the resistance of gas and, in a very minor quantity, the surface resistance of the anode to receive electrons, while another little small portion, as it was only later understood, was used to extract electrons from the cathode. It was then clear that the resistance of gas depended not only on its chemical nature and pressure, but also on the diameter of the tube and the amount of electric current flowing. The Geissler tube, as it was later called, was thought to replace an improved design of the already mentioned Nollet’s ‘‘electrical egg,’’ which had a glass bulb with negative and positive electrodes protruding through a wall (Fig. 8), previously designed by Ruhmkorf and the French physicist Jean-Antoine Quet (1810–1884) for carrying out similar electrical experiments. Unlike Geissler tubes, which were evacuated and sealed off, ‘‘electric eggs’’ were pumped out each time, and the valve was closed. If it is true that the possibility for changing gas and its pressure were the advantages exhibited by the electric egg, the Geissler tubes showed to be, as a whole, superior for the purposes of many experiments. A decisive factor for the proliferation of Geissler’s tubes was the second stage of his cooperation with Plücker (Fig. 9). When it began in 1857, shortly after Geissler had shown his vacuum pump and the tubes at the university, the reputations of both men were well consolidated and their activities strengthened and supplemented each other: Geissler with outstanding skills as a glassblower but missing out on formal education, and Plücker as a leading mathematician and physicist of the day, but aware of his lack of skills in the experimental work. After various employments at German universities, Plücker settled in Bonn as a Professor of Mathematics from 1836 until 1847, when he turned to experimental physics. His first subjects of research were taken from Faraday, whose nonmathematical experimental style he greatly respected. After working in the study of the magnetic properties of crystals, liquids, and gases, and more specifically on the anomalous magnetic behavior of uniaxial crystals in a magnetic field, closely related to Faraday’s researches on diamagnetism, Plücker became involved in researches on electrical discharges in vacuum tubes. One of the main problems tackled by Plücker and Geissler in the new field of research was the comparison of the two phenomena that Plücker formerly differentiated when discharge tubes were subjected to external forces, such as, for example, the influence of a strong magnet: the socalled ‘‘positive’’ light, which showed up in the space surrounding the anode, and aroused more attention because of its sparkling effects, and the ‘‘negative’’ light, a bright bluish light that was localized close to the surface of the cathode. As evacuation proceeded and pressure inside the tube decreased, the use of Geissler’s vacuum pump presented the first Vol. 103, No. 9, September 2015 | Proceedings of the IEEE 1679 Scanning Our Past Fig. 8. Electric egg. (a) Lights of different discharges. (b) Edmond Becquerel’s arrangement for electric discharges in oxygen (1839) [41]. clear vision of the phenomena by which the negative light spread into the surrounding space while the positive light faded away. The most important of the joint experiments of Geissler and Plücker, carried out in 1857, focused specifically on the influence of a magnet on the behavior of a gas discharge in a tube. The first result of the comparative investigation of the behavior of both lights under the influence of a strong magnet showed that the positive light behaved in a way analogous to a thin metallic wire stretched between the two terminals, as it had previously been documented by the Swiss physicist Auguste de la Rive (1801–1873). Its properties had then the possibility of being explained by Ampère’s laws for metallic conductors. On the other hand, the negative light, if extending from the cathode into the surrounding space, would be bent in agreement with Faraday’s ‘‘lines of magnetic force,’’ or magnetic field lines as they would be later known. The article where the results were reported was authored, however, only by Plücker [42], [43]. Working with typical Geissler tubes, 250 mm long, 10 mm wide, and provided with bulbs at each end enclosing the sealed-in electrodes and a large upright horseshoe electromagnet to the two limbs where an equal number of heavy windings were attached, both men were able not only to draw conclusions about the initially investigat1680 ed phenomena, but also about some unforeseen situations presented as ‘‘. . . the division of the light-stream, its decomposition at the negative electrode into an undulating flickering light and the extension of the stream from the positive electrode into a brilliantly illuminating fine point . . .’’ (Fig. 10). Further experiments by Geissler and scientists like Faraday and his compatriot William Crookes (1832– 1919) indicated that all individual gases or vapors would carry current, and that some of them would give off a fairly strong light. Geissler made tubes according to the specific fronts in which Plücker worked. For one of them, the observation and investigation of chemical reactionsVa new branch of science which he called ‘‘microchemistry’’Vfor example, Geissler prepared tubes filled with Fig. 9. Julius Plücker (1801–1868). Proceedings of the IEEE | Vol. 103, No. 9, September 2015 vapors of essential oils which decomposed under electric discharge. Geissler produced many different tubes, experimenting with several sizes, kinds of glass, gases, vapors, liquids, and pressures. In the 1880s, the production became massive, both as scientific instrument and entertainment devices. Around 1910, 12 years after neon’s discovery by the British chemists Sir William Ramsay (1852– 1916) and Morris W. Travers (1872– 1961) in London, the Geissler’s tube discharges evolved into commercial neon lighting thanks to the work of the French engineer and inventor Georges Claude (1870–1960). The tubes usually incorporated combinations of attractive shapes such as bells, bubbles, curlicues, twists, and bends. Some tubes were very elaborate and complex in shape, and would contain chambers within an outer casing. Several problems arose in the early years, mainly due to the difficulty of obtaining good quality glass over a long period, and the incompatibility of glasses made by different manufacturers. With certain gases the efficiencies of light emission realized were considerably higher than those of incandescent lamps. Nitrogen and carbon dioxide gave the best results. Mercury, sodium, sulphur, chlorides, bromides, and other vapors also produced light of various colors. The tubes were not always used for research but also as commercial novelties and entertainment devices, which occasionally generated Scanning Our Past Fig. 10. Drawings showing a magnet’s effect on gas discharges in Geissler’s tubes [42], [43]. criticism from researchers like the German Johann Christian Poggendorff (1796–1877) who, as editor of one of the most important scientific journal on physics at the time, Annalen der Physik, only believed in pure scientific work. Nevertheless Geissler expanded the production of these attractive tubes and sold them in many countries. Thanks to his skills and dexterity, Geissler participated in a select network of instrument makers and scientists who exchanged information and demonstrated their newest achievements both at large public exhibitions, fairs, and in each other’s laboratories or workshops. Starting in 1859, many tubes were dispatched by Geissler to countries in Europe, mainly France, England, and Germany, to the point where soon few university physical cabinets were without them. Researchers such as Faraday, Crookes, and Plücker’s pupil, Johann Wilhelm Hittorf (1824– 1914) [44], as well as instrument makers such as Ruhmkorff, and organizations devoted to scientific education and research, such as the Royal Institution of London, through its secretary Henry Bence Jones (1813– 1873), among many others, received important numbers of samples of the tubes. Experiments carried out with them led to many new discoveries in the next decades. The availability of Geissler tubes, a Ruhmkorff coil really catching the attention of continental scientists, and the spectacular effects obtained in experiments such as those described above renewed the interest of several scientists in the subject of gaseous discharge. One of them, for example, was Faraday, who, this time in the company of the British businessman and amateur scientist John Peter Gassiot (1797– 1877), Vice-President of the Royal Society at that time, carried out researches between 1856 and 1858 in order to try to reconcile the discharge phenomena with his own theory of electrical action. Most of their observations seemed to show reconciliation with his theory, although few cracks in its theoretical structure also began to appear. It was Gassiot who really made the experiments [45] and Faraday never wrote anything for publication from those observations [46]. In November 1862, Geissler joined Plücker on a journey to the Great London Exposition, where both had the opportunity to show their experiments to Faraday, Gassiot, Jones, the Irish General Sir Edward Sabine (1788–1883), and the physicist John Tyndall (1820–1893), among many others. The favorable response contributed to enhancement of the dissemination of the new technology and the distribution of the discharge tubes. Similar demonstrations were made in their native Germany, where those present included Poggendorff and the physicist Philipp von Jolly (1809– 1884), chemists Liebig and Friedrich Wöhler (1800–1882), and the Vol. 103, No. 9, September 2015 | Proceedings of the IEEE 1681 Scanning Our Past German instrument maker of Gustav Robert Kirchhoff (1824–1887) and Robert Wilhelm Bunsen (1811–1899), Carl August Steinheil (1801–1870). IV. CONCLUDING RE MARKS William Thomson, 1st Baron Kelvin, expressed in 1893: ‘‘If a first step towards understanding the relations between ether and ponderable matter is to be made, it seems to me that the most hopeful foundation for it is knowledge derived from experiment on electricity at high vacuum and if, as I believe is true, there is good reason for hoping to see this step made, we owe a debt of gratitude to the able and persevering workers of the last forty years who have given us the knowledge we have: and we may hope for more and more from some of themselves and from others encouraged by the fruitfulness of their labors to persevere in the work’’ [47]. Geissler was one of those workers. His mercury vacuum pump and innovative techniques for the construction of gas discharge tubes containing metal electrodes paved the way for future glow discharge experimentation, and outstanding technological applications in the latter part of the 19th century and the first decades of the 20th century. The puzzle of cathode rays that began with him and Plücker continued in the first stage with Hittorf, who suggested that the cathode was the source of an emanation that was not only electrically charged but also traveled in straight lines like rays of light; Crookes, who concluded in the 1870s that the current-carrying rays from the cathode were a torrent of charge electrified molecules of matter in an attenuated state not hitherto encountered; and the German scientist Gotthilf-Eugen Goldstein (1850– 1930), who threw much needed light on the atomic transformations involved in the phenomenon of gas discharges by discovering in 1876 the so-called ‘‘Kanal-Strahlen,’’ or positive rays [48]. Different scientists also in1682 scribed their theoretical and practical contributions in the decades that followed Röntgen’s discovery of X-rays, showing how to produce cathode rays in low pressure discharge tubes; how to focus, accelerate, and deflect them; and finally, how to convert these rays into light by slamming them into phosphor, and causing phosphor to emit light. Names such as Heinrich Hertz, who used some experimental results of his own investigationsV later proved to be incorrectVto demonstrate that cathode rays were electromagnetic radiation and not a stream of particles, Phillip Lenard who measured some properties of the cathode rays, the Frenchman Jean Baptiste Perrin (1870–1942), who demonstrated that the cathode rays were negatively charged, and J. J. Thomson, who by confirming Perrin’s experiments was led to discover the electron, among others, belong to this group of scholars. However, no matter how long the list may be, or how important the scientists’ inputs were, no one can question the character of Geissler’s work as a new starting point in this subject, which transformed the gas discharge research from a playful and fragmented field into a new branch of physical science and technology. The cathode ray tube, whose invention is usually credited to the German physicist Karl Ferdinand Braun (1850–1918), bears a strong resemblance to the original Geissler tubes. A quick look at Braun’s account of 1897 shows that both have a cathode and an anode, but, in addition, the cathode ray tube has a heater to warm the cathode, and also a fluorescent screen at the end of the tube with the anode. The anode in both has a positive voltage relative to the cathode, attracting the electrons pulled along by the electric field [49]. While Geissler’s and other cathode ray tubes previous to Braun’s work had produced uncontrolled cathode ray streams, Braun succeeded in producing a narrow stream of electrons directed by means of alternating Fig. 11. Geissler’s Honorary Doctorate diploma. (Credit: Courtesy Sandra Otto, Archives of the Rheinische Friedrich-Wilhelms-University of Bonn.) Proceedings of the IEEE | Vol. 103, No. 9, September 2015 Scanning Our Past voltages that could trace patterns on a fluorescent screen. The impact that Geissler had on the advance of original investigation of the subject of the gas discharge is not easy to measure, and his name is infrequently mentioned in connection with the numerous discoveries where his fruitful ideas have contributed in greater or lesser degree to successful results. Neither in his time, nor afterwards, did Geissler receive the homage that his contributions surely deserve. If it is true that the University of Bonn, on the occasion of its jubilee in 1868, rendered a tribute by bestowing on him the honorary title of Doctor of Philosophy (Fig. 11), he himself lamented that his work was not fully recognized. In a letter to Liebig dated February 2, 1858, Geissler complained that he had prepared and conducted most of the experiments, while Plücker only mentioned him as a ‘‘helping hand’’ in his publications [50]. Some current accounts on the state of the scientific research in Bonn in the second half of the 19th century [51] as well as reviews of the development of the cathode ray tube [52] fail to mention Geissler’s name. Geissler was able not only to bring about the practical realization of the many designs submitted to him, but, in a majority of cases, he planned and produced apparatuses of the most elegant construction and rigorous preci- rimental investigation to clear up the properties of cathode rays. In 1874, Franz Müller had joined the Geissler’s workshop and carried the firm into the early 20th century as ‘‘Geissler’s Nachfolger’’ (Fig. 12). The Geissler tubes were produced until the 1930s there by other glassblowers like Greiner & Friedrichs, Rudolf Pressler, and Richard Müller-Uri. h Acknowledgment Fig. 12. Geissler Nachfolger’s catalog, 1925. sion, involving a comprehension of physical laws to be expected only of someone with formal education, who has devoted his life to the solution of scientific problems. Heinrich Geissler died on January 24, 1879, in Bonn, at the age of 65, just before the great breakthrough of the vacuum tube technology, and the possibility of producing vacuums exceeding one millionth of an atmosphere opened up by Crookes, and Geissler’s radiometer work, which opened the door to a systematic expe- The author would like to thank Dr. G. Dörfel for his great help in the preparation of this paper and for his kind permission to reproduce the photograph of the Geissler’s tubes herein. He would also like to thank S. Otto from the Archives of the University of Bonn and R. Schäfer from the Bayerische Staatsbibliothek at Munich for providing a scan of the diploma of Geissler’s Honorary Doctorate and general information about Geissler’s correspondence with J. von Liebig, respectively. The valuable contribution of Hermann Knauer is also much appreciated. The author would like to express his gratitude to the anonymous reviewers of a draft of this paper and to the Editorial Staff of the Proceedings of the IEEE for their helpful comments and suggestions. SIMÓN REIF-ACHERMAN REFERENCES [1] K. Eichhorn, ‘‘Heinrich Geissler (1814–1879): His life, times and work,’’ Bull. Sci. Inst. Soc., no. 27, pp. 17–19, Dec. 1990. [2] F. Müller and G. Dörfel, ‘‘Zwischenwissenschaft und handwerk. Der glasinstrumentenbauer Heinrich GeiQler und seine schule,’’ Phys. J., vol. 13, no. 5, pp. 39–42, 2014. [3] T. H. N., ‘‘Heinrich Geissler,’’ Nature, vol. 19, no. 486, p. 372, 1879. [4] A. W. Hofmann, ‘‘Dr. Heinrich Geissler,’’ Ber. Dtsch. Chem. Ges., vol. 12, pp. 147–148, 1879. [5] G. Dörfel, ‘‘Heinrich GeiQler (1814–1879)V Einnachtrag,’’ Jahrbuch des Hennebergisch Fränkischen Geschichtsvereins, vol. 28, pp. 187–192, 2013. [6] E. Gerland and F. Traumüller, Geschichte der Physikalischen Experimentierkunst. Lepzig, Germany: Engelmann, 1899, p. 255. [7] J. Plücker and H. Geissler, ‘‘Studien über thermometrie und verwandte gegenstände (Thermometry and allied subjects),’’ Ann. Phys. (Berlin, Germany), vol. 86, pp. 238–279, 1852. [8] A. W. Blyth, Foods: Their Composition and Analysis: A Manual for the Use of Analytical Chemists and Others. London, U.K.: Ch. Griffin, 1896, p. 477. [9] A. Thurston, Pharmaceutical and Food Analysis, a Manual of Standard Methods for the Analysis of Oils, Fats and Waxes, Substances in Which They Exist; Together With Allied Products. New York, NY, USA: van Nostrand, 1922, p. 40. [12] N. H. de V. Heathcote, ‘‘Guericke’s sulphur globe,’’ Ann. Sci., vol. 6, no. 3, pp. 293–305, 1950. [13] T. Brundtland, ‘‘Francis Hauksbee and his air pump,’’ Notes Rec. Roy. Soc., vol. 66, no. 3, pp. 253–272, 2012. [14] T. Brundtland, ‘‘After Boyle and the Leviathan: The second generation of British air pumps,’’ Ann. Sci., vol. 68, no. 1, pp. 93–124, 2011. [15] F. Hauksbee, Physico-Mechanical Experiments on Various Subjects. LondonU.K.: Senex & Taylor, 1709, pp. 3–4. [10] J.-F. Picard, ‘‘Experience faire à l’observatoiresur la barometre simple touchant un nouveau phenomenequ’on y a découvert,’’ Le Journal des Sçavans, vol. 4, pp. 112–113, 1676. [16] F. Hauksbee, ‘‘An account of an experiment, touching the production of light within a globe glass, whose inward surface is lin’d with sealing-wax upon an attrition of its outside,’’ Philos. Trans. Roy. Soc. Lond., vol. 26, no. 313–324, pp. 219–221, 1708. [11] E. N. Harvey, A History of Luminescence. From the Earliest Times to 1900. Philadelphia, PA, USA: APS, 1957, pp. 271–273. [17] R. W. Home, ‘‘Francis Hauksbee’s theory of electricity,’’ Arch. Hist. Exact. Sci., vol. 4, no. 3, pp. 203–217, 1967. Vol. 103, No. 9, September 2015 | Proceedings of the IEEE 1683 Scanning Our Past [18] W. Wheatstone, ‘‘On the prismatic decomposition of electrical light,’’ J. Franklin Inst., vol. 22, no. 1, pp. 61–63, 1836. [19] E. Swedenborg, ‘‘Miscellanea observata circa res naturales et praesertim circa mineralia, ignem et montium strata (Miscellaneous observations: Connected with the physical sciences),’’ Lipsiae 1722 (reprinted translated from the Latin, 1976). [20] P. A. Redhead, ‘‘The ultimate vacuum,’’ Vacuum, vol. 53, pp. 137–149, 1999. [21] W. H. T. Meyer, Beobachtungen Über das Geschichtete Electrische Licht Sowie Über den Merkwü Rdigen EinfluQ des Magneten auf Dasselbe Nebst Anleitung zur Experimentellen Darstellung der Fraglichen Erscheinungen. Berlin, Germany: Büxenstein, 1858. [22] J. C. Poggendorf, ‘‘Uebereineneueeinrichtung der quecksilber-luftpumpe,’’ Ann. Phys., vol. 201, no. 5, pp. 151–160, 1865. [23] O. Lehmann and D. J. Frick, Physikalische Technik oder Anleitung zu Experimentalvorträgen Sowie zur Selbstherstellung Einfacher Demonstrationsapparate. Braunschweig, Germany: Friedrich Biemeg und Sohn, 1905, pp. 590–936. [24] A. Toepler, ‘‘Übereineeinfache barometer-luftpumpe ohne hähne, ventile und schädlichen Raum,’’ Dingler’s Polytechnisches J., vol. 163, no. 113, pp. 426–432, 1862. [25] H. Sprengel, ‘‘Researches on the vacuum,’’ J. Chem. Soc.vol. 18, pp. 9–21, 1865. [26] M. H. Hablanian, ‘‘Comments on the history of vacuum pumps,’’ J. Vac. Sci. Technol., A, vol. 2, no. 2, pp. 118–126, 1984. [27] K. Jousten, Ed., Handbook of Vacuum Technology Weinheim, Germany: Wiley, 2008, p. 8. [28] W. de la Rue and H. W. Müller, ‘‘Experimental researches on the electrical discharge with the chloride of silver battery,’’ Philos. Trans. Roy. Soc. London, vol. 169, pp. 155–241, 1878. [29] R. K. Waits, ‘‘Edison’s vacuum technology patents,’’ J. Vac. Sci. Technol., A, vol. 21, no. 4, pp. 881–891, 2003. [30] Anonymous, ‘‘Edison’s vacuum apparatus,’’ Sci. Amer., vol. 42, no. 3, pp. 34–35, 1880. [31] B. Park, A History of Electricity: The Intellectual Rise in Electricity. New York, NY, USA: Wiley, 1898, p. 508. [32] J. L. Heilbron, Electricity in the 17th and 18th Centuries: A Study in Early Modern Physics. Mineola, NY, USA: Dover, 1999, pp. 280–289. [33] C. C. Silva, ‘‘Jean Antoine Nollet’s contributions to the institutionalization of physics during the 18th century,’’ in Brazilian Studies in Philosophy and History of Science. An Account of Recent Works, D. Krause and A. Videira, Eds. Dordrecht, Germany: Springer-Verlag, 1911, pp. 131–140. [34] W. Watson, ‘‘An account of the phenomena of electricity in vacuo with some observations thereupon,’’ Philos. Trans. Roy. Soc. Lond.vol. 47, pp. 362–376, 1751–1752. [35] E. N. Hiebert, ‘‘Electric discharge in rarefied gases: The dominion of experiment. Faraday, Plucker, Hittorf,’’ in No Truth Except in the Details, M. J. Klein, A. J. Kox, and D. M. Siegel, Eds. Dordrecht, Germany: Kluwer, 1995, pp. 95–134. [36] T. W. Chalmers, ‘‘Historic researches,’’ in History of Physical and Chemical Discovery. New York, NY, USA: Scribner, 1952, p. 194. [37] C. Wheatstone, ‘‘An account of some experiments to measure the velocity of electricity and the duration of electric light,’’ Philos. Trans. Roy. Soc. Lond., vol. 124, pp. 583–591, 1834. [38] T. A. L. du Moncel, Notice sur l’appareil d’induction électrique de Ruhmkorff. Paris, France: Hachette, 1855. [39] W. R. Grove, ‘‘On the electro-chemical polarity of gases,’’ Philos. Trans. Roy. Soc. Lond., vol. 142, pp. 87–101, 1852. [40] A. A. Bright, Jr., The Electric-Lamp Industry. Technological Change and Economic Development from 1800 to 1947. Boston, MA, USA: MacMillan, 1947, p. 220. ABOUT THE AUTHOR Simón Reif-Acherman was born in Palmira, Colombia, in 1958. He received the Chemical Engineer degree from the Universidad del Valle, Cali, Colombia, in 1980. Since then, he has been with the School of Chemical Engineering, Universidad del Valle, where he currently holds the position of Titular Professor. He is the author of more than 15 articles. His research interests include history of physics, chemistry and technology, and development of learning tools in engineering education. 1684 Proceedings of the IEEE | Vol. 103, No. 9, September 2015 [41] M. Pouillet, Éléments de Physique Experimentale et de Météorologie, 7eme ed. Paris, France: Hachette, 1856. [42] J. Plücker, ‘‘Ueber die einwirkung des magneten auf die elektrischen entladungen in verdünnten gasen,’’ Ann. Phys., vol. 103, no. 88–106, pp. 151–157, 1858. [43] J. Plücker, ‘‘On the action of the magnet upon the electrical discharge in rarified gases,’’ Philos. Mag., vol. 16, pp. 119–135, 1858. [44] F. Müller, ‘‘Johann Wilhelm Hittorf and the material culture of nineteenth-century gas discharge research,’’ Brit. J. Hist. Sci., vol. 44, no. 2, pp. 211–244, 2011. [45] J. P. Gassiot, ‘‘The Bakerian LectureVOn the stratifications and dark band in electrical discharges as observed in torricellian vacua,’’ Philos. Trans. Roy. Soc. Lond., vol. 148, pp. 1–16, 149, 137–160, 1858. [46] L. Pearce-Williams, Michael Faraday. New York, NY, USA: Da Capo Press, 1987, pp. 474–479. [47] W. Thomson (Lord Kelvin), ‘‘Presidential address,’’ Proc. Roy Soc., vol. 54, pp. 376–394, 1893. [48] M. E. Maia, I. Serra, and I. M. Peres, ‘‘The gas discharges in history and teaching of physics and chemistry,’’ Travaux de Laboratoire, tome L, vol. 2, pp. 22–30, 2011. [49] K. F. Braun, ‘‘Ueber ein Verfahren zur Demonstration und zum Studium des zeitlichen Verlaufes variabler Ströme,’’ Ann. Phys., vol. 296, no. 3, pp. 552–559, 1897. [50] Bayerische Staatsbibliothek, ‘‘Letter From Heinrich GeiQler to Justus von Liebig,’’ Munich, Germany. [51] G. Schubring, ‘‘The rise and decline of the Bonn natural sciences seminar,’’ Osiris, vol. 5, pp. 56–93, 1989. [52] I. Falconer, ‘‘Corpuscles, electrons and cathode rays: J. J. Thomson and the ‘Discovery of the electron’,’’ Brit. J. Hist. Sci., vol. 44, no. 3, pp. 241–276, 1987.