Jean-Baptiste Schwilgue

Acknowledgement to my correspondent Mr. Denis Roegel, Professor at Loria, France, for his important works on Schwilgué’s calculating machines.
Georgi Dalakov

Portrait of Jean-Baptiste Schwilgué
Jean-Baptiste Schwilgué (1776-1856)

In 1844 the French engineer Jean-Baptiste Schwilgué from Strasbourg, together with his son Charles-Maximilien, patented a key-driven calculating machine, which seems to be the third key-driven machine in the world, after these of James White and Luigi Torchi, but was certainly the first popular keyboard calculator. Similar machines will be invented and manufactured by many inventors in the next 60 years. Moreover, several years later Schwilgué devised a bigger specialized calculating machine.

Additionneur Schwilgué (Schwilgué’s Adder)

Before starting the creation of his calculating machines, Schwilgué made a number of preliminary studies years before, such as a design of the computus mechanism (Easter computation) in 1816, of which he built a prototype in 1821. This mechanism, whose whereabouts are now unknown, could compute Easter following the complex Gregorian rule. The astronomical part is unusually accurate: it indicates leap years, equinoxes, and much more astronomical data.

Schwilgué himself was trained as a clockmaker, but also became a professor of mathematics, weights and measures controller, and an industry man, whose particular focus was on improving scales. After the completion of his famous astronomical clock of Strasbourg Cathedral in the early 1840s and following a change in the French patent laws, Schwilgué, with or without his son, patented several inventions, including the above-mentioned small adding machine. This machine appeared in the 1846 catalog of Schwilgué’s tower clock company, but was most probably devised some 10 years ago, in the middle 1830s.

The key adder of Schwilgué, a device from 1846 ((© Historical Museum Strasbourg)
The key adder of Schwilgué, a device from 1846, carrying the Nr. 15 (© Historical Museum Strasbourg)

As of now, several copies of the machine are known: one is in a private collection (Boutry-Ungerer family), one (dated 1846) in the Strasbourg Historical Museum (the machine (see the upper image) is in a poor state and carries the Nr. 15), and one (dated 1851) is in the collections of the Swiss Federal Institute of Technology in Zurich (see the lower images).

The calculating machine of Schwilgué in Zurich (Courtesy of the Swiss Federal Institute of Technology)
The calculating machine of Schwilgué in Zurich (Courtesy of the Swiss Federal Institute of Technology)
A side view of the Schwilgué's machine in Zurich (Courtesy of the Swiss Federal Institute of Technology)
A side view of Schwilgué’s machine in Zurich (Courtesy of the Swiss Federal Institute of Technology)

Like other machines of this kind (so-called single-column adders), the device of Schwilgué was intended to add a single digit at a time, i.e. the unit column is entered first, then the tens, the hundreds, the thousands, and so on, certainly rather cumbersome task (as every partial sum had to be recorded on paper and the sum eventually performed), which greatly limits the usefulness of such devices.

The inside of calculating machine of Schwilgué in Zurich (Courtesy of the Swiss Federal Institute of Technology and Mr. Denis Roegel)
The inside of calculating machine of Schwilgué in Zurich (Courtesy of the Swiss Federal Institute of Technology and Mr. Denis Roegel)
Under the top plate of calculating machine of Schwilgué (Courtesy of the Swiss Federal Institute of Technology and Mr. Denis Roegel)
Under the top plate of calculating machine of Schwilgué (Courtesy of the Swiss Federal Institute of Technology and Mr. Denis Roegel)

In closed status, the machine is a box with nine numbered keys, an opening showing two or three digits in two parts, and two knurled knobs. It is 25.5 cm long, 13.6 cm wide, and 9.5 cm tall (without the knobs), weight 3.3 kg. The inside of one of the machines is almost identical to the patent drawing (see the next figure).

The patent drawing of the calculating machine of Schwilgué
The patent drawing of the small calculating machine of Schwilgué

Schwilgué’s machine has three main functions: addition, carrying, and setting.

The upper figure shows figures I, II, III, and IV of Schwilgué’s patent. Figure IV shows how the keys operate. Each key can move downward by an amount corresponding to its value and moves the wheel G, but only when the key is released. (Schwilgué stated, however, that this can be changed, to work on key pressing). This wheel meshes with wheel H (horizontal in Figure III), and the unit wheel moves counterclockwise by as many digits as the pressed key. The unit wheel is the wheel on the right of Figure II. It contains each digit three times.

The units and tens wheels can be set using the knurled knobs, so that before an addition the openings would show 00. On the Zurich machine, resetting the wheels is made easier by pins located under the wheels. When the knobs are pushed downwards, R or U disengage, but the pins are put in the way of stops so that one merely has to turn the knobs until it is no longer possible.

It may seem surprising to see such an invention, long after more sophisticated calculating machines such as Thomas’s Arithmometre (1820), or even the Roth machine (1841). It must, however, be understood that Schwilgué’s machine was never meant as a general adding machine.

Schwilgué, who had obtained a number of patents since the 1820s, was no doubt well aware of Thomas’s machine and other general calculating machines. We know, for instance, that Schwilgué had a copy of the description of Roth’s machines, as well as a copy of a history of calculating instruments published in 1843 by Olivier. It is possible that these articles were an incentive for Schwilgué to build his calculating machine, or they may have been part of his research for his own machine.

Unlike that of the general-purpose calculating machines, Schwilgué’s purpose was to ease a particular operation, the hand checking of addition. In these cases, only small values were handled, and Schwilgué didn’t bother to build a machine with 10-digit inputs, although it could probably have been done with his carrying mechanism. Instead, Schwilgué could see that the existing machines, although powerful in principle, were of little use for everyday accounting. Schwilgué’s machine was designed to fill that gap by using keys to input numbers. Schwilgué could see their potential, even though he never claimed to have invented the keyboard, as keyboards already existed on musical instruments.

The calculating machine of Schwilgué has several other interesting features (some are mentioned only in the patent):
The one, that has already been mentioned, is the use of a clock escapement-like way of adding the carry, although Schwilgué never qualified it that way. This feature seems also present on Schilt’s machine.

The patent drawing also shows that the keyed figures are only taken into account when the keys are released. However, Schwilgué stated explicitly that both are possible, either upon pressing or upon release and that the patent covers both.

Schwilgué also mentioned an interesting feature which he called “tout ou rien” (all or nothing). Besides the name, which alludes to binary logic and may have been borrowed from Julien Le Roy in the context of repeating watches that had to ring all chimes or none, it was here an optional feature ensuring that a digit was only taken into account when the key had been completely pressed. However, according to Schwilgué, this was not really needed as one learned quickly to operate the machine and not to make mistakes. A similar safety measure was introduced as late as 1913 in the ill-fated E-model of the Comptometer of Dor Felt. On that, an automatic blocking device prevents errors and forces the operator to repeat pressing a key that was not adequately depressed.

Schwilgué’s Calculator of Sequences

It is known also, that in the middle 1840s Schwilgué constructed a bigger specialized calculating machine, a solid brass device with 36 result wheels, kept now in the collection of Historical Museum Strasbourg (see the lower photo). This machine was advertised at “300 to 400” francs in 1846 (about three months’ salary for a common laborer of the period), and at “400 to 500” francs in 1847, but it seems unlikely that any was sold because it was too specialized.

Schwilgué's Calculator of Sequences (© Historical Museum Strasbourg)
Schwilgué’s Calculator of Sequences (© Historical Museum Strasbourg)

This specialized machine had a single purpose—to calculate multiples of some value using additions, and on 12 digits (i.e. the machine works with 12-digit integers, and it computes their multiples in sequence). In the 1830s and 1840s Schwilgué made several gear-cutting machines, which position is given by angles at regular intervals. To be able to calculate the angles with a large accuracy, Schwilgué wanted to compute the fractions 1/p, 2/p, 3/p…, p/p on 12 places. Thus the output of the calculating machine (values were copied on paper) can be used as an input for the gear-cutting machine.

The machine is a weight-driven device with a modular design and includes 12 almost identical blocks (one for each place), a command arbor, and a command block. A crank is provided (normally not used), for rewinding the machine and clearing carries.

Once the machine is rewound, a detent is shifted and the mechanism does one addition, then stops. This operation is repeated until the machine is rewound. After each computation, the values are copied on paper.

The command block is similar to a striking clock with two 54-teeth wheels, a pinion of 9 leaves, a second wheel of 47 teeth, and a double threaded worm. The weight is attached to a string that is wound around a drum driving one of the 54 teeth wheels, and this wheel meshes with the second 54 teeth wheel, as well as with the pinion. The second 54 teeth wheel drives the command arbor. The pinion drives the second wheel and the worm which leads to a brake and an arm stopped by the detent. When the detent is released, the arm is freed and the mechanism turns, until the detent again meets a notch on the 54 teeth wheel of the command arbor. There is also a notch in the other 54 teeth wheel, and the two work together as in common striking clocks.

Schwilgué's bigger calculating machine (© Denis Roegel)
Schwilgué’s bigger calculating machine (© Denis Roegel)

When the command block is triggered, the 54 teeth wheels perform one turn and so does the command arbor. This arbor is tangent to the 12 blocks and carries 24 arms, organized helically, two per block. It is a natural consequence of the relative position of the blocks, of the arbor, and of the need to sequentialize the additions at each place: first the units, then the tens, etc. The arrangement of the computing blocks dictates the structure of the command arbor.

Each block displays three digits and the three sets of 12 digits represent three 12-digit numbers. One is a simple counter, and it will show 000000000000, 000000000001, 000000000002, etc. The other is a constant and will never change during an operation. It will for instance store a value such as 076923076923 for 1=13. The third one will merely show the multiples of the constant. There are therefore two independent, but synchronous, functions: the counter, and the multiple. These functions are synchronous so that one value (the counter) could serve as an entry to the second (the multiple). In the case of the counter, the machine has to add one to the units, and to propagate the carries. In the case of the constant, the constant must be added to the stored sum, and carries have to be propagated. Each of these two functions is obtained by two arms of the command arbor. One arm is for incrementing the counter, the other is for adding one digit of the constant to one digit of the sum.

The prototype of the machine was probably constructed in 1844, but the earliest known plans are from 1846. Later the machine seems to have slightly evolved and the above-mentioned device follows plans dated 1852.

Schwilgue’s bigger machine should be remembered as an exceptional example of his engineering genius and as a rare example of an early specialized calculator, full of subtle features.

Biography of Jean-Baptiste Schwilgué

Jean-Baptiste Schwilgué, portrait by Gabriel-Christophe Guérin from 1843
Jean-Baptiste Schwilgué, portrait by Gabriel-Christophe Guérin from 1843

Jean-Baptiste Sosime Schwilgue was born on 18 Dec. 1776 in Strasbourg, France, in a house located at the intersection of rue Brûlée and rue de la Comédie. He was the second son of the civil servant François-Antoine Schwilgue (1749-1815) and Jeanne Courteaux (1750-1784). François-Antoine was native from Thann in Grand Est (Schwilgue (or Schwilcke) family settled in Thann centuries ago), and came to Strasbourg to serve as valet de chambre in l’Intendance royale d’Alsace à Strasbourg. Jeanne Courteaux was native from de Solgne (Moselle). Jean-Baptiste had an elder brother, Charles Joseph Antoine, born on 10 Oct. 1774, who became a doctor and professor of medicine in Paris, but died only 33 years old on 7 Feb. 1808. His mother Jeanne also died young on 13 April 1784, when Jean-Baptiste was only 8, and his father married second time in June 1785 to Marie-Anne Kauffeisen (1746-1809).

As a boy, Jean-Baptiste showed great interest in mechanics, and with the help of the simplest tools available to him, he produced various machines and instruments, by which he made special improvements that he had conceived. He was very fond of looking at the Strasbourg Cathedral astronomical clock, made in the 1570s by Konrad Dasypodius (1532-1600), and often stood for hours before it, thinking about putting this highly sophisticated watch (which at the time was very badly or not at all functional anymore), again in the workable state.

In 1789, after the outbreak of the French Revolution, the father of Jean-Baptiste lost his position and moved from Strasbourg to Sélestat (Schlestadt), Alsace (he died there on 14 Feb. 1815), where Jean-Baptiste continued his studies, devoting himself, especially to mathematics. Besides his studies, he learned the art of watch-making, entering a watch-making shop as an apprentice.

Anne Marie Thérèse Hihn-Schwilgué
Anne Marie ‘Thérèse’ Hihn-Schwilgué

In 1796 Jean-Baptiste became self-employed and married Anne Marie “Thérèse” Hihn (1778-1851, see the nearby image), a daughter of the confectioner Charles Hihn and Thérèse Baldenberger, on 25 April in Sélestat.

Eight children, three boys and five girls, were born from this marriage: Marie Thérèse (1797-1848), Jean-Baptiste (1798-1855), Charles-Maximilien (1800-1861), Françoise (1802-1806), Louise (1804-1864), Adélaïde (Adèle) (1806-1850), Sébastien “Alexandre” (1811-1836), and Marie “Clémentine” Emilie (1812-1878).

In 1807 Jean-Baptiste was appointed official at the district’s office of Sélestat (he was the town clockmaker and verifier of weights and measurements), and also a professor of mathematics at the local college, which he retained until he moved to Strasbourg in 1827. In the meantime, he was always occupied with the Strasbourg astronomical clock, and around 1820 he invented a mechanical church calendar with a precise determination of the movable festivals according to the Gregorian. This church calendar, which he had carried out in a smaller model (15×20 cm), he brought to the French Academy of Sciences in 1821, and even presented it personally to King Louis XVIII.

The third astronomical clock of Strasbourg Cathedral
The third astronomical clock of Strasbourg Cathedral

The masterpiece of Schwilgué’s life was the third astronomical clock of Cathédrale Notre-Dame de Strasbourg. As early as 1827, Schwilgué had submitted to the city council of Strasbourg a report on the condition of the clock, together with three proposals on the repair of the same; the first two, while retaining certain parts of the old clock, and the third, for a completely new clock. But it was not until 1836, after lengthy negotiations, that the city council of Strasbourg came to a final decision on the restoration of the clock, and was only approved by the higher administrative authority at the beginning of 1838. As the agreement was signed in May 1838, in June, Schwilgué set to work on the new clock. Together with his son Charles and his apprentices and later partners—brothers Albert and Theodor Ungerer, he was able to finish this assignment in July 1842. On 2 October 1842, on the occasion of the 10th Congress of Sciences in France in Strasbourg, the clock was set in motion for the first time, and Schwilgué was congratulated on all sides for the great success of the work which he had undertaken. In November 1842, a large banquet was held in his honor, and on 31 December 1842, a grand feast with a solemn parade through the town to commemorate the fortunate prosperity of the work erected by Schwilgué.

In 1835 Schwilgue was appointed Knight of the Legion of Honour and in 1853 on a report of the Minister of Education and Religious Affairs he obtained the rank of Officer of the Legion of Honour.

Jean-Baptiste Sosime Schwilgue died 79 years old on 5 December 1856 in Strasbourg (see below the gravestone of Jean-Baptiste Schwilgué and his wife Anne Marie “Thérèse” Hihn). His son Charles inherited his father in the workshop (and in 1857 wrote a book about his famous father, named Notice sur la vie, les travaux et les ouvrages de mon pere, J. B. Schwilgue), but in 1858 he was paralyzed by a stroke, and died three years later.

The gravestone of Jean-Baptiste Schwilgué and his wife Anne Marie "Thérèse" Hihn in Strasbourg
The gravestone of Jean-Baptiste Schwilgué and his wife Anne Marie ‘Thérèse’ Hihn in Strasbourg

Denis Roegel: An Early (1844) Key-Driven Adding Machine, IEEE Annals of the History of Computing, vol. 30, №1, pp. 59-65, January-March 2008)