Jean-Baptiste Schwilgué

In 1844 the French Jean-Baptiste Sosime Schwilgué (1776–1856) from Strasbourg, together with his son Charles, patented a key-driven calculating machine (brevet d'invention N° 624, pris le 24 décembre 1844), which seems to be the second key-driven machine in the world, after this of Luigi Torchi. In contrast to the machine of Torchi, however, the Schwilgué's is a simple adding machine for single columns adding. Similar machines will be invented and manufactured by many inventors in the next 60 years.

Jean-Baptiste Schwilgué was a famous french engineer and inventor from 19th century, Officier de la Légion d'Honneur, best known as the architect of the last astronomical clock in Cathédrale Notre-Dame de Strasbourg, built from 1838 until June 24, 1843 (see the nearby photo).
Schwilgué made a number of preliminary studies years before, such as a design of the computus mechanism (Easter computation) in 1816, and 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 was trained as a clockmaker, but also became professor of mathematics, weights and measures controller, and an industry man, whose particular focus was on improving scales. After the completion of the clock and following a change in the French patent laws, Schwilgué, with or without his son, patented several inventions, including a small adding machine (French patent number 623, applied in December 1844). This adding machine appeared in the 1846 catalogue of Schwilgué’s tower clock company.

As of now, several copies of the machine are known: one is in a private collection (Boutry-Ungerer family), at least two are in a Strasbourg museum, and one dated 1851 is in the collections of the Swiss Federal Institute of Technology in Zurich (see the lower photos).

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)

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)

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. 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

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). This wheel meshes with wheel H (horizontal on 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. After all, keyboards already existed on musical instruments.

The calculating machine of Schwilgué has some 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 only in 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.