Typographic unit

(Fournier's printed scale of his point system, from Manuel Typographique, Barbou, Paris 1764, enlarged) However, the basic idea of the point system – to generate different type sizes by multiplying a single minimum unit calculated by dividing a base measurement unit such as one French Royal inch – was not Didot's invention, but Fournier's.

Didot just made the base unit (one French Royal inch) identical to the standard value defined by the government.

In Britain and the United States, many proposals for type size standardization had been made by the end of 19th century (such as Bruce Typefoundry's mathematical system that was based on a precise geometric progression).

However, the American Point System standardized finally in 1886 is different from Hawks' original idea in that 1 pica is not precisely equal to 1⁄6 inch (neither the Imperial inch nor the US inch), as the United States Type Founders' Association defined the standard pica to be the Johnson Pica, which had been adopted and used by Mackellar, Smiths and Jordan type foundry (MS&J), Philadelphia.

Binny & Ronaldson was one of the oldest type foundries in the United States, established in Philadelphia in 1796.

The equipment is thought to be that which Benjamin Franklin purchased from Pierre Simon Fournier when he visited France for diplomatic purposes (1776–85).

The official standard approved by the Fifteenth Meeting of the Type Founders Association of the United States in 1886 was this Johnson pica, equal to exactly 0.166 inch.

[citation needed] Comparing a piece of type in didots for Continental European countries – 12 dd, for example – to a piece of type for an English-speaking country – 12 pt – shows that the main body of a character is actually about the same size.

The TeX typesetting system uses the abbreviation dd for the earlier definition, and nd for the metric new didot[2]