Louis Troncet

Human beings make life so interesting. Do you know, that in a universe so full of wonders, they have managed to invent boredom.
Terry Pratchett

Louis Troncet (1850-1920)
Louis-Joseph Troncet (1850-1920)

After the slide adders of Claude Perrault, César Caze, and Heinrich Kummer, in 1889 the French teacher, school director, inventor, scientist, and writer Louis-Joseph Troncet (1850-1920), created his version of this type of calculator, which he called Arithmographe. Troncet’s invention became so popular that the term “Troncet-type” is often used to refer to this class of devices. The device was in production for almost 30 years. Millions of units of this type were sold. It was on the market until the 1970s!

Louis-Joseph Troncet was a holder of four French patents for calculating devices: Brevet №123135 from 21.03.1878, №133106 (22.10.1879), №171473 (3.10.1885), and №197579 (18.04.1889) (never published as fees were not paid). The first patent (from 1878) was for a slide adder with dials, called Numerateur, which has never been put in production (see the lower patent drawing of the device).

The patent drawing of the Numerateur of Troncet
The patent drawing of the Numerateur of Louis Troncet

The devices of Troncet are typical of the small, usually hand-held, stylus-driven adding machines. They are often known as crook or cane adders, because of the shape of the input slots. The operator moved a stylus up or down the slot n spaces to add or subtract the digit n. If there was not enough space to move n places, the stylus was forced to go over the hook and effect a carry to the next digit.

The next three patents are for different versions of the Arithmographe (see the patent drawing of the third version from 1889).

The patent drawing of the third Arithmographe of Troncet
The patent drawing of the third Arithmographe of Troncet

Namely, the third version of the Arithmographe (see the lower photo) featured so clever and reliable construction, that became a market hit at the end of the 19th and the beginning of the 20th century. The first devices were produced by Librairie Larousse and were sold normally in a small notebook with a set of multiplication tables.

The Arithmographe of Troncet
The Arithmographe of Louis Troncet

The Arithmographe was made of paper and copper alloy (copper, brass, bronze), its dimensions are 10 x 13,6 x 0,5 cm; the weight was 300 g. A good description of the workings of the device can be seen in the manual (see the lower image) from a very popular in the US analog of the Arithmographe, the Baby Calculator. There is also a detailed description of Arithmographe in the book Фон-Бооль, Приборы и машины для механическаго производства арифметических действий. Описание и оценка счетных приборов и машин, see description of Аритмографъ Тронсе.

The Arithmographe of Troncet used flat metal bands with notched edges to represent digits. These bands were moved with the stylus to enter numbers. The instrument has seven crook-shaped columns that reveal the edges of eight notched bands. The crook at the top of each groove is designed to ease carrying or borrowing.

Eight holes below the columns labeled ADDITION, show the results of the addition operation. Eight holes above the columns labeled SOUSTRACTION, show the results of the subtraction operation. There is no zeroing mechanism.

The manual of Baby Calculator
The manual of Baby Calculator

Louis Troncet manufactured and sold another calculating device, a dial adder, called Totalisateur (see the lower photo), which was a circular adding device (The Scottish pastor Brown’s Rotula Arithmetica from the 1690s can be seen as the archetype of all of these concentric toothed disk-adding devices). It however didn’t become a market hit, in contrast with the Arithmographe.

The Totalisateur of Troncet
The Totalisateur of Louis Troncet

Biography of Louis-Joseph Troncet

Louis-Joseph Troncet (1850-1920)
Louis-Joseph Troncet (1850-1920), a drawing by his son Antony

Louis-Joseph Troncet was born on 16 November 1850, in Montierchaume, a village near Chatearoux, in the Indre department of central France. He was the son of Joseph Troncet, cultivateur-cantonnier (farmer and cantonier), and his wife Marie Robrolle-Troncet, а housekeeper. In 1859, Marie Troncet gave а birth to a boy, Henri, who died five days later. The next day died Marie, so Louis lost his mother only nine years old.

As a boy, Troncet was a brilliant student and obtained a Brevet Supérieur, then a certificate d’Aptitude Pédagogique at the Normal School in Chatearoux, and then was appointed as a school director in the village of Buzançais (30 km NW of Chatearoux). His career continued as a teacher and school director in Reuilly (50 km NE of Chatearoux), then in Saint-Florentine (near Vatan) from 1900 to 1912, then from 1912 until his retirement in Selles sur Nanon, a village close to Buzançais.

The school in Saint-Florentine, a postcard from 1901. The man at the window is supposed to be Louis Troncet.
The school in Saint-Florentine, a postcard from 1901. The man at the window is supposed to be Louis Troncet.

In addition to his job as a teacher, Troncet did mathematical, scientific, and educational research that led him to many inventions (besides his calculating instruments), as follows:
– HOROMETER—a dial displaying the local time in different countries of the world (in 1904)
– CHRONOGRAPHE—an instrument, which for a given date establishes concordance with the different calendars existing in the world
– COSMOSPHERE—an instrument, which indicates after orientation the relative positions of the stars according to the place where we are on Earth (in 1914)
– ROSE MAGNETIQUE—a compass rose that turns exactly, that is to say, all the points of which turn themselves towards the points of the horizon which it represents (in 1915)

Troncet also published numerous books and booklets in various topics, mainly in the area of domestic animals and diseases (some co-written with other authors), including textbooks for intuitive reading which have been translated into several languages. Let’s mention only: Calculateur mécanique instantané. Arithmographe Troncet. Larousse, 1890; Horomètre, cadran donnant l’heure universelle. G. Gambart, 1904; La Basse-cour. La poule, le dindon, la pintade, le pigeon, le canard, l’oie, le cygne, le paon, le faisan, le lapin, le léporide, le cobaye. Races, alimentation, hygiène, accidents et maladies…; Arboriculture pratique. Larousse, 1895; Le Jardin potager. Larousse, 1895; Premier livre encyclopédique: cours de lectures intuitives. Larousse; Le bétail: le cheval, l’âne, le mulet, le bardot, le boeuf, le mouton, la chèvre, le porc, le chien, le chat… Larousse, 1902; Le bétail. Larousse, 1895; Les Animaux de France utiles ou nuisibles. Larousse, 1901.

Troncet was a titular member of the Société Astronomique de France (from 1910), and lecturer at l’Institut Géographique de Paris. At the end of the 1890s, Troncet left his post as a school director in Reuilly, to collaborate in Paris in the writing of the great Larousse dictionary and of the universal Larousse magazine, and became editor-in-chief of the magazine Après l’Ecole founded in 1885 by René Leblanc.

Anna Arthémise Berthouly-Troncet
Anna Arthémise Berthouly-Troncet

Troncet was a holder of many awards. In 1899 the Ministry of Education promoted him to Officer of the Academy and Officer of Public Instruction. At the Universal Exhibition of 1900, Troncet received from the International Jury the diploma and silver medal of the Press of Education. In 1903 he was awarded a medal for his scientific inventions from Fabricants et Inventeurs Français. He was a holder of a medal of the House LAROUSSE.

On 14 November 1876, Louis-Joseph Troncet married in Buzançais to Anna Arthémise Berthouly (see the nearby portrait). The family had three boys: Louis Joseph Marie (born 9 August 1877), Félix Maurice Antony (born 23 May 1879), and Georges François Fernand (born 31 January 1884). Antony Troncet (1879-1939) became a known French painter, illustrator, engraver, and poet. Joseph Troncet became the Head of the Department at the Paris City Hall. Fernand became a schoolteacher like his father but unfortunately died young.

Louis-Joseph Troncet died on 15 February 1920, in his family home on rue de l’Indre in Chateauroux. His wife Anna Arthémise will follow him in 1930.

Fernand (left photo of a drawing from his brother) and Antony Troncet (1879-1939) as 18 y.o. in 1897
Louis Troncet’s younger sons: Fernand (left photo of a drawing from his brother Antony ) and Antony (1879-1939) as 18 y.o. in 1897