Truchet & Types

Truchet and the typographic point

Sébastien Truchet, 1657-1729.

The 1998 ATypI congress was held in the city of Lyon.
Lyon is also the hometown of father Sébastien Truchet who was born there in 1657. Few people realise the key role that Truchet played in the history of typography.
Here, he is remembered as the true inventor of the typographic point.

At the end of the 17th century, body sizes were not measured but were given names instead (just as today's bold typefaces are referred to as "heavy", "light", or "demi bold" without being really measured). These names were often based on the title of books in which the characters were used for the first time. For example, "Cicero"was the name given to the body sizes of characters used to print Cicero's Epistles while the characters in the book "City of God", written by the father of the Church, were known as "Saint Augustin". They could also derive from their appearance: the English "pica" comes from the Latin pica (magpie) since the first printed book used clearly distinguished blacks and whites, like the plumage of the magpie bird. Other names stem from the origin of the characters (e.g. "Parisienne"), their function (the French "Canon", English "brevier" or German "Missal"); or f rom their relative size ("Petit Romain", "Gros-Canon") since there was an implicit scale between these sizes (a "little Canon", for example, was twice as large as a "Saint Augustin"). However, sizes differed widely from one foundry to another and it was very difficult to mix types produced by different foundries or even by a single foundry for that matter.

The end of the 17th century also coincided with the age of Enlightenment. Envious of the achievements of foreign countries, Colbert, a minister of Louis XIV, decided in 1692 to prepare a compendium on existing arts, crafts and trades and appointed four scientists to head this work: abbot Bignon, Jacques Jaugeon, Gilles Filleau des Billettes and father Sébastien Truchet. They began work and quickly completed several illustrated descriptions of existing trades and professions. In 1699, Louis XIV elected them to the Academy where they continued their work under the direction of Réaumur. However, in 1750 (Truchet was already dead!), while no volume of the Description des métiers had yet been published, Diderot and D'Alembert announced the release of their Encyclopédie. This vexed the Academy which in turn published seventy-three volumes and some two thousand printing plates. Collections of this Description des Métiers are very rare and this work is quite unknown.

Let us return to the year 1693 when the Bignon Commission undertook its compendium of trades and professions beginning with printing (sic) "that art that will preserve all others".

The members of the commission, in particular Truchet, studied (using a recently invented microscope) characters known at that time and proposed three successive systems to quantify types in which a series of body sizes were defined in regular increments on the principle of the "line", a unit of measurement used by silversmiths and equivalent to 1/12 of the official inch. Although in the 17th century the metric system had not been introduced, in 1670 father Mouton submitted to the Academy a unit of length, the virga, equal to a thousandth of the distance segmented along the earth's meridian by one minute of angle. Units of length then in use included the toise, which comprised two aulnes (roughly equivalent to today's metre) which comprised 3 feet ; the foot (0,32484m) was divided into 12 inches (2,707 cm); each inch was divided into 12 lines (de 2,256 mm) and each line into 12 metric points (de 0,188 mm). The problem was that these values varied from place to place. The values given here are known as king ("roi") values. To complicate matters further, the English feet and inches were slightly different !

The initial project was conceived in 1694. It is based on several principles:

Typefaces are measurable. Their measurement is based on a legal unit of length.
The scale of possible body sizes is governed by a given rule: the bodies are deducted from the previous body by adding an increment in accordance with a geometric progression; the bodies are 7,5 9 10,5 12, then 15 18 21 24 and so on. The real size of the type is therefore 7,5 lines seconds, 9 line seconds and so on.

This final rule is given here in modern mathematical terms:

Type sizes are expressed in multiples of c_i of the second line of the inch of the "roi" (i.e. 1/12 × 1/12 of an inch, today's 0.1879583 mm).
The body sizes are defined as follows: c₀=7,5
c_i=c_i-1 + 1,5 × 2^i÷4

The second project, conceived in 1695, was based on the 1/24 line, while the third project used a far smaller unit, the 1/204 line, the equivalent of today's 0,011057 mm. This is roughly equivalent to 2,300 dpi. While this value is one we may dream of, it continues to amuse the punch casters since no mechanical tool is able to provide such high precision. Fournier, 50 years later, used 7 parts whereas Truchet proposed 204, declaring that (sic) "these rules refer to the concept of infinitely small characters that only the imagination can attain! Consequently, are so many squares necessary to form a O shape which is round ?". The surprising choice of 204 is perhaps related to the sum product of 12 × 17 where 12 is the duo decimal base and where 17 might be equal to the number of lines (16) encountered in the lower case designs cast by Simoneau plus 2/2 (two half lines for the shoulders).

However, this invention did not have an immediate sequel. Perhaps it was too "academic". All existing punches would have had to be re-cast and all types re-minted ! In addition, since the system that Truchet proposed was not totally identical to the one used at that time (his system did not fully reflect the deformed reality of the day), Truchet invented new names for character sizes such as "la Petite Royale" (body size 12) or "Le Bourbon" (body size 36). Moreover, the members of the Chambre syndicale des imprimeurs (Printers' Guild) probably had no knowledge of this research since at their request the king issued a decree on 28 February 1723 which laid down the paper height of types as well as the official relationships between the former names.

Proposed new scale of types and metrics (including cap height, x-height, descenders, head letters (written by Truchet himself).

Pierre-Simon Fournier (nicknamed "the Young") was familiar with the work of Truchet (since he had ridiculed it) and applied the concept of proportions but by adapting the scale of typefaces to existing character body sizes. This gave rise to the Fournier point of 1737 which, unfortunately, is not based on a legal unit. The Fournier point was closer to the pica than the Truchet point.

Didot in turn incorporated Truchet's concept and standardised the typographic point in 1783 (based on the 1/72 of the French inch but with practically the same progressions as Truchet). Regarding Truchet's typographic point, the punches had to be re-cast, which explains why many printers continued to use Fournier's point until the 20th century.

Background reading:

Andrew Boag, « Typographic measurement: a sequence of events from Moxon to 1992 », Typography papers, vol. 1, Reading University, 1996, 105-121.
Pierre-Fournier dit le jeune, Manuel typographique utile aux gens de lettres, et à ceux qui exercent les différentes parties de l'Art de l'Imprimerie, chez l'auteur, Paris, 1764. New english edition: The Manuel Typographique of Pierre-Simon Fournier le jeune together with Fournier on Typefounding An English translation of the Text by Harry Carter in facsimile, With an Introduction and Notes by James Mosley, trois volumes ; Darmstadt, 1995.
André Jammes, La naissance d'un caractère : le Grandjean -- la réforme de la typographie royale sous Louis XIV, Librairie Paul Jammes (1961) et Promodis, 1985.
James Mosley, « French academicians and modern typography: designing new types in the 1690s », Typography papers, The Univrsity of Reading, 1997, vol. 2, pp.5-29.

Jacques André, formaly Irisa/Inria-Rennes, France
Denis Girou, CNRS,Orsay

October 1998 (English version by 5/5 Rennes).

Truchet The Point Romain du roi Tiling systems