Units of lengths

1 februari 2010

The units of length used in seventeenth century western Europe were all derived from the ancient Roman measurement system, which, it was claimed, was based on the dimensions and proportions of the ideal human being.

The Roman system of measures was devided as follows:

  • Digitus (1/16 pes) – 1.85 cm
  • Uncia (1/12 pes) – 2.46 cm
  • Palmus (1/4 pes) –  7.39 cm
  • Palmus maior (3/4 pes) –  22.18 cm
  • Pes – 29.57 cm
  • Palmipes (1¼ pedes) – 36.97 cm
  • Cubitus (1½ pedes) 44.36 cm
  • Gradus/pes sestertius (2½ pedes) – 73.94 cm
  • Passus (5 pedes) – 147.87 cm
  • Actus (120 pedes) – 35.49 m
  • Mille passum (5000 pedes) – 1478.70 m

After the demise of the Roman Empire, this system essentially remained intact, although the Latin terms were often replaced by names in the vernacular. However, because there were no means to determine and maintain identical measurements over a wide area, in the Middle Ages (and long afterwards), the various units of length were defined locally. For example, a town council would determine how large a foot or yard was in its own jurisdiction. Other definitions were used in other towns. This meant that, if a length was described of so many feet, it was also necessary to explain which foot was being used. However, as the demand for a uniform metric system grew, due to the increase in trade and communication over large distances, some local units of measurement gained influence outside the local area.

In the Dutch provinces, the Rhineland units of measurement were predominantly used for surveying and scientific purposes. The mathematician Willebrord Snel van Rooyen (Snellius) of Leiden used this system in 1615 and 1621 to measure the circumference of the earth. The basic unit of the Rhineland measurement system was the Rhineland roede (measuring rod), the length of which was recorded by two notches made near the entrance to Leiden’s town hall. These notches were lost when the town hall was destroyed by fire in 1929 and were replaced by two iron studs when it was rebuilt. A copy of the original Rhineland rod, a long iron staff, was formerly held at the Leiden Observatory, and can now be seen in Leiden’s Boerhaave Museum.

The commonly used Dutch measures were:

  • lijn (1/12 duim) – 0.21802 cm
  • duim (1/12 voet) – 2.61622 cm
  • voet – 31.39465 cm
  • roede (12 voeten)  376.73580 cm

The commonly used French measures were:

  • ligne (1/12 pouce) – 0.22558 cm
  • pouce (1/12 pied)- 2.70700 cm
  • pied – 32.48394 cm
  • toise (6 pieds) – 194.90366 cm

The commonly used English measures were:

  • line (1/12 inch) – 0.21166 cm
  • inch (1/12 foot) – 2.53995 cm
  • foot – 30.47945 cm
  • yard (3 feet) – 91.43835 cm