Leonardo Torres Quevedo

Cable car at the mount Ulía, inaugurated in 1907.

Torres' experimentation in the field of cableways and cable cars began very early during his residence in the town of his birth, Molledo. There, in 1887, he constructed the first cableway to span a depression of some 40 metres (130 ft). The cableway was about 200 metres (660 ft) across and pulled by a pair of cows, with one log seat. This experiment was the basis for his first patent application in Spain, "Un sistema de camino funicular aéreo de alambres múltiples" ("A multi-wire suspended aerial system"),[17] for a cable car with which he obtained a level of safety suitable for the transport of people, not only cargo. The patent was later extended to other countries: United States, Austria, Germany, France, United Kingdom, and Italy.[18] Torres' cable cars used an innovative multi-cable support system, in which one end of a cable is anchored to fixed counterweights and the other (through a system of pulleys) to mobile counterweights. With this system the axial force of the cables via is constant and equal to the weight of the counterweight, regardless of the load in the shuttle. What will vary with this load is the deflection of the via cables, which will increase by raising the counterweight. Thus, the safety coefficient of these cables is perfectly known, and is independent of the shuttle load. The resulting design is very strong and remains safe in case of a support cable failure. Later, he constructed a cableway over the Río León in Valle de Iguña, Spain, that was faster and motorized, but still used solely for the transport of materials, not of people.[19][20][21]

In 1889 Torres presented his cableway in Switzerland,[22] a country very interested in that form of transport owing to its geography, and which was already starting to use cable cars for bulk transport in the Klimsenhorn-Pilatus Kulm line. However, he put his project on hold for a few years due to both rejection by Swiss engineers and comments and caricatures that appeared in the press of that country.[23] On 30 September 1907, Torres put into operation a pioneer cableway suitable for the public transportation of people in San Sebastián, the Mount Ulia aerial ropeway. The journey was 280 meters, with a drop of 28 meters, lasted for just over three minutes, and the gondola had the capacity to board up to 18 people on each trip. The execution of the project was the responsibility of the Society of Engineering Studies and Works of Bilbao.[24][25][26]

Aero car over the whirlpool on Niagara river, Canada.

The positive results of this type of cable car led him to develop his most famous cable car, the Spanish Aerocar in Niagara Falls in Canada. The cableway of 550 meters in length is an aerial cable car that spans the whirlpool in the Niagara Gorge on the Canadian side. It travels at about 7.2 kilometres per hour (4.5 mph). The load per cable via is 9 tonnes (9.9 short tons), with a safety coefficient for the cables of 4.6.[27] It was constructed between 1914 and 1916. For its construction and assembly, the Niagara Spanish Aerocar Company Limited was set up from the Society of Engineering Studies and Works, both companies promoted by Torres, with a capital of $110,000 (roughly $3.2 million in 2022),[28] and a planned concession of 20 years. The construction was directed by Torres' son, Gonzalo Torres Polanco.[29] It completed its first successful tests on the 15th of February in 1916 and was officially inaugurated on the 8th of August, opening to the public the following day. The cableway, with small modifications, runs to this day with no accidents worthy of mention, constituting a popular tourist and cinematic attraction.[30] A plaque, mounted on a boulder in front of Aero Car Gift Shop recalls this fact: International Historic Civil Engineering Site. THE NIAGARA SPANISH AEROCAR. A tribute to the distinguished Spanish Engineer who designed the Niagara Spanish Aerocar. This was only one of his many outstanding contributions to the engineering profession. Engineer Leonardo Torres Quevedo (1852–1936). Constructed 1914–1916. CSCE. The Canadian Society for Civil Engineering. 2010. Asociación de Ingenieros de Caminos, Canales y Puertos de España. Spanish aerial ferry of the Niagara.[31]

Torres' Algebraic Machine

Since the middle of the 19th century, several mechanical devices were known, from integrators, multipliers, to the Analytical engine of Charles Babbage. The work of Torres in this matter is framed within this tradition, which began in 1893 with the presentation of the "Memória sobre las máquinas algébricas" ("Memory about algebraic machines") at the Spanish Royal Academy of Sciences in Madrid.[32] This paper was commented in a report by Eduardo Saavedra in 1894 and published in the Revista de Obras Públicas.[33] Torres developed a first model of the machine, and Saavedra recommended that the final project of the device be financed.[34] Torres' calculating machine was considered in its time as an extraordinary event in the course of Spanish scientific production. In 1895 he presented "Machines algébriques", accompanied by his demonstration model, at the Bordeaux Congress of the Association pour l'Avancement des Sciences, and in Paris in the Comptes rendus de l'Académie des Sciences.[35] Later on, in 1900, he presented a more detailed work, "Machines á calculer" ("Calculating machines") at the Paris Academy of Sciences. The commission, informed favorably by Marcel Deprez, Henri Poincaré and Paul Appell, asked the academy for its publication,[36][37] highlighting: "... Mr. Torres has given a theoretical, general and complete solution to the problem of the construction of algebraic and transcendental relations by means of machines..."[38]

These machines examined mathematical and physical analogies that underlay analogue calculation or continuous quantities, and how to establish mechanically the relationships between them, expressed in mathematical formulae. The study included complex variables and used the logarithmic scale. From a practical standpoint, it showed that mechanisms such as turning disks could be used endlessly with precision, so that changes in variables were limited in both directions.[39][40][41] On the practical side, Torres built a whole series of analogue calculating machines, all mechanical. These machines used certain elements known as arithmophores which consisted of a moving part and an index that made it possible to read the quantity according to the position shown thereon.[42] The aforesaid moving part was a graduated disk or a drum turning on an axis. The angular movements were proportional to the logarithms of the magnitudes to be represented. Between 1910 and 1920, using a number of such elements, Torres developed a machine that was able to compute the roots of arbitrary polynomials of order eight, including the complex ones, with a precision down to thousandths. The machine calculated the following formula: ${\displaystyle \alpha ={\frac {A_{1}X^{a}+A_{2}X^{b}+A_{3}X^{c}+A_{4}X^{d}+A_{5}X^{e}}{A_{6}X^{f}+A_{7}X^{g}+A_{8}X^{h}}}\,}$ where X is the variable and A₁ ... A₈ is the coefficient of each term. Considering the case of α = 1, it becomes the following formula, and the root of the algebraic equation can be obtained: ${\displaystyle A_{1}X^{a}+A_{2}X^{b}+A_{3}X^{c}+A_{4}X^{d}+A_{5}X^{e}-A_{6}X^{f}-A_{7}X^{g}-A_{8}X^{h}=0\,}$

Fusee sans fin (endless spindle)

By calculated each term on a logarithmic scale, they can be calculated only by sums and products like A₁ + a × log(X), which can handle a very wide range of values, and the relative error during calculation is constant regardless of the size of the value. However, in order to calculate the sum of each term, it is necessary to accurately obtain log(u + v) from the calculated values log(u) and log(v) on a logarithmic scale. For this calculation, Torres invented a mechanism called "endless spindle" ("fusee sans fin"), a complex differential gear with a helical gear, which allowed the mechanical expression of the relation ${\displaystyle y=\log(10^{x}+1)}$. Putting log(u) - log(v) = log(u/v) = V, and using u/v = 10 V, calculate log(u + v) using the following formula: ${\displaystyle \log(u+v)=\log(v(u/v+1))=\log(v)+\log(u/v+1)=\log(v)+\log(10^{V}+1)\,}$,[43] the same technique which is the basis of the modern electronic logarithmic number system.

In addition to this machine, Torres devised other with a small computing using gears and linkages around 1900 to obtain the complex number solution of the quadratic equation X² - pX + q = 0.[44] The machines are kept in the Torres Quevedo Museum at the School of Civil Engineering of the Technical University of Madrid.[45]

Airship Astra-Torres No.1 at an air show in 1911

Torres with a model of his airship in 1913

In 1902, Torres started the project of a new type of dirigible that would solve the serious problem of suspending the gondola, applying for a patent in France for ‘Perfectionnements aux aerostats dirigibles’ ("Improvements in dirigible aerostats"),[46][47] complemented, with a "Note sur le calcul d’un ballon dirigeable a quille et suspentes interieures" ("Note on the calculus of a dirigible balloon with interior suspension and keel") which was presented together to Madrid and Paris’ Academies of Science.[48][49] Opposite to the usual cylindrical envelope, and with the objective of minimizing its stress and subsequent permeability, Torres conceived a trilobed envelope with three longitudinal cables (ropes) placed in the intersection of every two lobes. Inside the envelope, and on the basis of those three cables, a longitudinal frame of triangular cross section was to be completed, made up of non-rigid ropes, permeable fabric curtains, metal cables and longerons. Longitudinal cables and frame would ‘rigidify’ altogether through the excess of pressure level of the gas, so that, when inflated, it would act as an internal rigid structure. A system known as "auto-rigid".[50] By the end of that year the report at Paris's Academy of Science was included in the French journal L’Aerophile, and a summary in English was published in the British The Aeronautical Journal.[51][52]

In 1904, Torres was appointed director of the Centre for Aeronautical Research in Madrid, "for the technical and experimental study of the air navigation problem and the management of remote engine maneuvers".[53]

In 1905, with the help of Alfredo Kindelán, he directed the construction of the first Spanish dirigible in the Army Military Aerostatics Service, located in Guadalajara. Once the construction was successfully completed in 1908, the new airship, which received the name of Torres Quevedo, carried out several test flights. As a result, a collaboration began between Torres and the Société Astra led by the French engineer Édouard Surcouf, which managed to buy the patent with a cession of rights extended to all countries except Spain, in order to make possible the construction of the dirigible in its country. So, in 1911, the construction of dirigibles known as the Astra-Torres airships was begun and Torres would receive royalties of 3 francs for every m³ of each airship sold.[54]

The Astra-Torres airship attached to a portable mooring post, 1913.

To find a resolution to the slew of problems faced by airship engineers in docking dirigibles, Torres also drew up designs for a ‘docking station’ and made alterations to airship design. In 1910, Torres proposed the idea of attaching an airship's nose to a mooring mast and allowing the airship to weathervane with changes of wind direction. The use of a metal column erected on the ground, the top of which the bow or stem would be directly attached to (by a cable) would allow a dirigible to be moored at any time, in the open, regardless of wind speeds. Additionally, Torres' design called for the improvement and accessibility of temporary landing sites, where airships were to be moored for the purpose of disembarkation of passengers. The final patent was presented in February 1911 in Belgium, and later to France and the United Kingdom in 1912, under the title "Improvements in Mooring Arrengements for Airships".[55][56][57]

Statue of Leonardo Torres Quevedo at the Museum of Aeronautics and Astronautics (Madrid).

In Issy-les-Moulineaux (south-west of Paris) in February 1911, the trials of ‘Astra-Torres no.1’ were successful and had a capacity of 1600m³. It was faster, more stable and more manoeuvrable than all the systems before it. It won the ‘Deperdussin’ prize and the French army incorporated it into their operations. In 1913, the handing over of the Astra-Torres XIV (the HMA.No 3 to the Royal Naval Air Service) meant international recognition for the system with this ship beating the world speed record for an airship registering 83.2 km/h during the reception trials, a speed which reached 124 km/h with the wind in its favour. Other Astra-Torres dirigibles followed, including the Pilâtre de Rozier (Astra-Torres XV) named after the aerostier Jean-François Pilâtre de Rozier, which at 23,000 m3 was the same size of the German ‘Zeppelins’ and could reach speeds of around 100 km/h. The distinctive trilobed design was widely used during the First World War (1914–1918) by the Entente powers for diverse tasks, principally convoy protection and anti-submarine warfare.[58][59] This type of envelope was employed in the United Kingdom in the Coastal, C Star, and North Sea airships.[60]

In 1919, Torres designed, based on a proposal of the engineer Emilio Herrera Linares, a transatlantic dirigible, which was named Hispania,[61] aiming to claim the honor of the first transatlantic flight for Spain. Owing to financial problems, the project was delayed and it was the Britons John Alcock and Arthur Brown who crossed the Atlantic non-stop from Newfoundland to Ireland in a Vickers Vimy twin-engine plane, in sixteen hours and twelve minutes.[62][63]

The success of the trilobed blimps during the war even drew the attention of the Imperial Japanese Navy, who acquired the Nieuport AT-2 in 1922, with almost 263 ft long, maximum diameter 54 ft and with a hydrogen capacity of 363,950 ft 3.[64] After Torres' patent expired that year, many airships continued to be built with ideas inherited from this non-rigid design.[65]

Telekino: transmitter.

Telekino: receiver.

Torres was a pioneer in the field of remote control. He began to develop a new system around 1901 or 1902, as a way of testing his airships without risking human lives. For its device, he chose the name Telekino as a combination of two Greek words: tele which means "at distance" and kino which means "movement", resulting both together "movement at distance", which was what Torres wanted to obtain. Between 1902 and 1903, the invention titled "Systéme dit Télékine pour commander à distance un mouvement mécanique" ("Means or method for directing mechanical movements at or from a distance") applied for patents in France,[66] Spain,[67] and Great Britain.[68] On 3 August 1903, he presented the Telekino at the Paris Academy of Science, together with a detailed memory and a practical demonstration to its members,[69] For the construction of this initial prototype, Torres received help from Gabriel Koenigs, director of the Mechanics Laboratory of the Sorbonne, and Octave Rochefort, who collaborated by providing wireless telegraphy devices.[70]

The Telekino has three different parts: a wireless telegraph receiver, a multi-position rotary switch and two servomotors that can be used to drive a mechanical system. The signal transmitted by electromagnetic waves, is received by the antenna and is transformed into electric pulses by a coherer. Each pulse drives an electromagnet, which closes its secondary circuit causing the multi-position switch unit to go one step forward. This operation is repeated automatically as many times as the number of signal impulses. When the multi-position switch reaches its final position, the battery supplies current to the chosen servomotor terminal. Then, the servomotor is put in motion causing a known and previously defined action. Torres realized that in order to achieve a finite but not limited set of actions based on a binary system as the telegraph was, (with only two states, on and off), it was necessary to create a limited number of codewords through a sequence of binary states. The problem, at that time, was the impossibility of having a synchronisation mechanism able to detect the end of one character and the beginning of the next. In this situation, the only way to solve this difficulty was using an asynchronous synchronisation method based on the change in the telegraph signal state. The final proposal was as simple as using a code based on the number of pulses consecutively sent; so, the action, e.g. number 1, corresponded to one pulse, to two pulses corresponded the action number 2, to three pulses the action number 3 and so on.[71] Torres was able to select different positions for the steering engine and different velocities for the propelling engine independently. He was also able to act over other mechanisms such a light, for switching it or not, and a flag, for raising or dropping it, at the same time. Specifically, Torres was able to do up to 19 different actions with his prototypes.[72]

From 1904 Torres chose to conduct initial Telekino testings, first in an electric three-wheeled land vehicle[73] in the Beti Jai fronton of Madrid, with an effective range of just 20 to 30 meters, which has been considered the first known example of a radio-controlled unmanned ground vehicle (UGV).[69] The Spanish engineer José Echegaray described the Telekino as the origin of Torres' automatics. For Echegaray, "nobody moves" the Telekino. "It moves automatically", it is an automaton of "a certain intelligence, not conscious, but disciplined". He defined it as "a material apparatus, without intelligence, interpreting, as if it were intelligent, the instructions that are communicated to it."[74][75] In 1905, Torres tested a second model of the Telekino located in a boat in the pond of the Casa de Campo in Madrid, achieving distances of up to about 250 m. From the terrace of the Club Marítimo del Abra, and with the assistance of the president of the Provincial Council and other authorities, an experiment was carried out with the Telekino remotely controlling the maneuvers of the electrically powered launch Vizcaya.[76] On 25 September 1906, in the presence of the king Alfonso XIII and before a great crowd, he successfully demonstrated the invention in the port of Bilbao, guiding the launch Vizcaya from the shore with people on board, demonstrating a standoff range of 2 km.[77] The positive results of those experiences encouraged Torres to apply to the Spanish government for the financial aid required to use his Telekino to steer submarine torpedoes, a technological field which was just starting out. His application was denied, which caused him to abandon the development of the Telekino.[78]

In 1907, Torres introduced a formal language for the description of mechanical drawings, and thus for mechanical devices, in Vienna. He previously published "Sobre un sistema de notaciones y símbolos destinados a facilitar la descripción de las máquinas" ("System of notations and symbols intended to facilitate the description of the machines") in the Revista de Obras Públicas.[79] According to the Austrian computer pioneer Heinz Zemanek, this was equivalent to a programming language for the numerical control of machine tools.[80] He defined a table of symbols, a collection of rules and, as usual in his works, applied them to an example. This symbolic language reveals Torres' main capacities, both his ability to detect a problem, in this case a social problem of origin and its technical consequences, as well as his capacity for creation – invention – to give a rational, properly technical response. As Torres said: "Babbage and Franz Reuleaux – and I suppose others as well, although I don't have news of them – have tried, without any success, to put remedy to this inconvenience; but although these eminent authors have failed, should not be a sufficient reason to abandon such an important effort".[81]

As a member of the steering committee of the Board for Expansion of Studies and Scientific Research (Junta para Ampliación de Estudios e Investigaciones Científicas) established in 1907 to promote research and scientific education in Spain,[82] Torres played a leading and decisive role in the creation of three keys state agencies to understand the impulse that institution gave to experimentation, both in the field of education and in research, regardless of the discipline: the Laboratory of Automation (1907) — of which he was named director,[83] the construction of instruments – the Laboratories Association (1910) – the union of state laboratories and workshops – and the Institute of Science Materials (1911) – the budget allocation. He not only built his own inventions, but also provided services and support to universities and researchers of the Board. The Laboratory of Automation produced the most varied instruments, such as the spectrographic equipment of Ángel del Campo and Miguel A. Catalán, the interferometer of Manuel Martínez Risco, the stalagmometer of Juan Negrín, the microtome of Santiago Ramón y Cajal and the X-ray spectrometer of Blas Cabrera, among others.[84][85]

"El Ajedrecista" #1 (The Chessplayer), complete view.

"El Ajedrecista" #2, interior view.

In early 1910, Torres began to construct a chess automaton he dubbed El Ajedrecista (The Chess Player). As opposed to The Turk and Ajeeb, El Ajedrecista had a true integrated automation and could automatically play a king and rook endgame against the king from any position, without any human intervention[86]

The pieces had a metallic mesh at their base, which closed an electric circuit that encoded their position in the board. When the black king was moved by hand, an algorithm calculated and performed the next best move for the white player.[87] The automaton does not deliver checkmate in the minimum number of moves, nor always within the 50 moves allotted by the fifty-move rule, because of the simple algorithm that calculates the moves. It did, however, checkmate the opponent every time.[88] If an illegal move was made by the opposite player, the automaton would signal it by turning on a light. If the opposing player made three illegal moves, the automaton would stop playing. The device has been considered the first computer game in history.[89]

It created great excitement when it made its debut, at the University of Paris in 1914.[90] Its internal construction was published by H. Vigneron in the French magazine La Nature.[91][92] It was widely mentioned in a Scientific American supplement as "Torres and His Remarkable Automatic Devices. He Would Substitute Machinery for the Human Mind", on November 6, 1915.[93][94]

An example game where White checkmates the black King, following Torres' algorithm. Recorded in Portable Game Notation:

[FEN "8/8/1k6/8/R7/8/5K2/8 w - - 0 1"]

1. Rh4 Kc5 2. Kf3 Kd5 3. Ke3 Kd6 4. Rh5 Kc6 5. Ke4 Kd6 6. Rg5 Kc6 7. Kd4 Kd6 8. Rg6+ Kd7 9. Kd5 Ke7 10. Rh6 Kf7 11. Ra6 Ke7 12. Rb6 Kf7 13. Ke5 Ke7 14. Rb7+ Kd8 15. Ke6 Kc8 16. Rh7 Kb8 17. Rg7 Ka8 18. Kd6 Kb8 19. Kc6 Ka8 20. Kb6 Kb8 21. Rg8#

Torres' son, Gonzalo, showing the automaton to Norbert Wiener at the 1951 Paris Cybernetic Congress.

A second version was constructed under the supervision of his son Gonzalo, and was presented in Paris in 1922. It was more elegant and technically perfected. The mechanical arms to move pieces were replaced for electromagnets located under the board.[95] It also included a sound effect, with a voice recording announcing checkmate when the computer won the game.[96]

The advanced machine was introduced to a greater audience at the 1951 Paris Cybernetic Congress and explained to Norbert Wiener.[97] El Ajedrecista also defeated Savielly Tartakower at the Congress, being the first Grandmaster to lose against a machine.[98] Heinz Zemanek played against this chess machine at the Brussels World Fair in 1958, described it as "a historical witness of automaton artistry that was far ahead of its time". According to Zemanek, Torres designed a very clever six-part algorithm for the end game, which was implemented using levers, gears, and relays.[99]

It has been commonly assumed (see Metropolis and Worlton 1980) that Charles Babbage’s work on a mechanical digital program-controlled computer, which he started in 1835 and pursued off and on until his death in 1871, had been completely forgotten and was only belatedly recognized as a forerunner to the modern digital computer. Ludgate, Torres y Quevedo, and Bush give the lie to this belief, and all made fascinating contributions that deserve to be better known.

— Brian Randell, presentation at MIT (1980), printed in Annals of the History of Computing, IEEE (October 1982)[100]

Leonardo Torres Quevedo (1917). Portrait by Joaquín Sorolla at the Hispanic Society of America in New York City.

In 1914, Torres published his most outstanding work, "Ensayos sobre Automática. Su definición. Extensión teórica de sus aplicaciones" ("Essays on Automatics. Its Definition – Theoretical Extent of Its Applications"), in which he took up the subject of what he called Automatics, "another type of automaton of great interest: those that imitate, not the simple gestures, but the thoughtful actions of a man, and which can sometimes replace him". Torres drew a distinction between the simpler sort of automaton, which has invariable mechanical relationships and the more complicated, interesting kind, whose relationships between operating parts alter "suddenly when necessary circumstances arise". Such an automaton must have sense organs, that is, "thermometers, magnetic compasses, dynamometers, manometers", and limbs, as Torres called them, mechanisms capable of executing the instructions that would come from the sense organs. The automaton postulated by Torres would be able to make decisions so long as "the rules the automaton must follow are known precisely".[101][102]

The paper provides the main link between Torres and Babbage. He gives a brief history of Babbage's efforts at constructing a mechanical Difference Engine and Analytical Engine. He described the Analytical Engine as exemplifying his theories as to the potential power of machines, and takes the problem of designing such an engine as a challenge to his skills as an inventor of electromechanical devices. The paper contains a complete design (albeit one that Torres regarded as theoretical rather than practical) for a machine capable of calculating completely automatically the value of the formula ${\displaystyle a^{x}(y-z)^{2}}$, for a sequence of sets of values of the variables involved. It demonstrates cunning electromechanical gadgets for storing decimal digits, for performing arithmetic operations using built-in function tables, and for comparing the values of two quantities. The whole machine was to be controlled from a read-only program (complete with provisions for conditional branching), represented by a pattern of conducting areas mounted around the surface of a rotating cylinder.[100]

The paper also introduced the idea of floating-point arithmetic, which historian Randell says was described "almost casually",[100] apparently without recognizing the significance of the discovery. He did it the way following:

"Very large numbers are as embarrassing in mechanical calculations as in usual calculations (Babbage planned 50 wheels to represent each variable, and even then they would not be sufficient if one does not have recourse to the means that I will indicate later, or to another analogue). In these, they are usually avoided by representing each quantity by a small number of significant figures (six to eight at the most, except in exceptional cases) and by indicating by a comma or zeros, if necessary, the order of magnitude of the units represented by each digit.

Sometimes also, so as not to have to write a lot of zeros, we write the quantities in the form n x 10${\displaystyle ^{m}}$.

We could greatly simplify this writing by arbitrarily establishing these three simple rules:

I. n will always have the same number of digits (six for example).

II. The first digit of n will be of order of tenths, the second of hundredths, etc.

III. One will write each quantity in the form: n; m.

Thus, instead of 2435.27 and 0.00000341682, they will be respectively, 243527 ; 4 and 341862 ; −5.

I have not indicated a limit for the value of the exponent, but it is obvious that, in all the usual calculations, it will be less than one hundred, so that, in this system, one will write all the quantities which intervene in calculations with eight or ten digits only."[103][104] The format that Torres proposed shows the need for a fixed-sized significand as is presently used for floating-point data.[105]

The paper ends with a comparison of the advantages of electromechanical devices that were all that were available to Babbage. It establishes that Torres would have been quite capable of building a general-purpose electromechanical computer more than 20 years ahead of its time, had the practical need, motivation, and financing been present.[106]

Torres Quevedo's 1920 Electromechanical Arithmometer, which used a remote typewriter to send commands to an electromechanical calculator and to print its results once computed.

Torres went ahead to prove his theories with a series of working prototypes. He demonstrated twice, in 1914 and in 1920, that all of the cogwheel mechanisms of a calculating machine like that of Babbage could be implemented using electromechanical parts. His 1914 analytical machine used a small memory built with electromagnets, capable of evaluating p × q – b.[100]

In 1920, to celebrate the 100th anniversary of the invention of the arithmometer, he presented at a Paris conference the "Arithmomètre Electroméchanique" ("Electromechanical Arithmometer"), which consisted of an arithmetic unit connected to a (possibly remote) typewriter, on which commands could be typed and the results printed automatically[100] (e.g. "532 × 257" and "= " from the typewriter). This calculator was not programmable, but was able to print the numerical value of the answer.[107] From the user interface point of view, this machine can be regarded as the predecessor of current computers that use a keyboard as an input interface. In terms of usage, remote calculation by extension of electric wires is also assumed,[108] and it is considered to be a rudimentary system such as the current online system that uses communication lines. Torres had no thought of making such a machine commercially, viewing it instead as a means of demonstrating his ideas and techniques.[109] Furthermore, in a 1920 paper on electromechanical arithmometers,[110] he pointed out the need to represent continuous numbers as finite discrete values for processing and judgment in several automatic machines,[111] which corresponds to current digital processing.

Caricature of Leonardo Torres Quevedo in the newspaper La Libertad (1923).

In addition to the aforementioned inventions, Torres patented, among others, the "Coordinate Indicator" (1901) for guiding people for cities by a mechanical system of signals, which he proposed for Madrid and Paris under the name of "Guide Torres",[112][113] the "Dianemologo" (1907), a machine to copy, without the need to resort to shorthand, any speech to as it is pronounced,[114] "Deformable Fusiform Balloons" (1914),[115] and "Railway Interlocks T.Q." (1918), an interlock of his own design to protect the movement of trains within a certain area.[116][117]

On 30 July 1913, he designed the "Buque-Campamento" ("Camp-Vessel"),[118] a dirigible balloon carrier with a mooring mast and a hold large enough to house up to two inflated units, and hydrogen cylinders. Torres had thought of the possibility of combining aeronautics with the navy in this way, offering his patent to Vickers Limited, although the latter did not show any interest in the project.[119] In 1916 Torres patented in Spain a new type of catamaran which was conceived as a steel multihull vessel, receiving the name of "Binave" (Twin Ship).[120] He applied for the patent in the United Kingdom with the title "Improvements in Ships" in 1917,[121] and it was built in Bilbao in 1918, where it carried out its first tests. He introduced important innovations in this design, such as two 30 HP Hispano-Suiza marine engines, or the ability to modify its configuration when sailing, positioning two rudders at the stern of each float, and placing the propellers aft too.[122][123]

In the last years of his life, Torres turned his attention to the field of educational disciplines, to investigate those elements or machines that could help educators in their task. From 1922 to 1930 he patented improvements on typewriters,[124] marginal pagination of manuals,[125] and, especially, the "Puntero Proyectable" ("Projectable Pointer"),[126] and the "Proyector Didáctico" ("Didactic Projector").[127] The Projectable Pointer was based on the shadow produced by an opaque body that moves close to the projected plate, being this shadow used as a pointer. To do this, he designed an articulated system that allowed the speaker to move a point or points next to the projection plate, at will, which made it possible to mark the areas of interest on the transparency.[128] The Didactic Projector improved the way slides were placed on glass plates for projection.[129]

In the early 1900s, Torres learned the international language Esperanto, and was an advocate of the language throughout his life. From 1922 to 1926, he participated in the work of the International Committee on Intellectual Cooperation of the League of Nations,[134] proposing the following motion on the first day of the meeting: "The Committee, convinced of the usefulness of an artificial auxiliary language to facilitate scientific relations between different peoples, establishes a subcommittee in charge of studying , with the help of experts, the various solutions that have been proposed". Although almost half of the Committee members were in favor of Esperanto, the motion met with determined opposition from some other participants. In 1925 Torres participated as the official representative of the Spanish government in the "Conference on the Use of Esperanto in Pure and Applied Sciences" held in Paris, together with Vicente Inglada Ors and Emilio Herrera Linares. That same year, he joined to the Honorary Committee of the Spanish Association of Esperanto (HEA), founded by Julio Mangada.[135][136]

Mis inventos y otras páginas de vulgarización by L. Torres Quevedo (1917).

• López-García, Rafael and Ceccarelli, Marco (2023). Distinguished Figures in Mechanical Engineering in Spain and Ibero-America, Springer Nature. pp. 321–357. ISBN 978-3031310751
• Romana García, Manuel; Durán Cermeño, Consuelo; Pascual Nicolás, María (2023). Leonardo Torres Quevedo. Miradas a un inventor célebre. Cinter Divulgación Técnica. ISBN 978-84-125610-3-6.
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• Torres y Quevedo, "Arithmometre Electromechanique," Bull. de la Societe d Encouragement for l'Industrie Nationale, Vol. 119, 1920, pp. 588–99, reprinted in Randell, Brian, Origins of Digital Computers: Selected Papers, Springer-Verlag, Berlin, 1982.