---
title: "History of the metric system"
chunk: 6/10
source: "https://en.wikipedia.org/wiki/History_of_the_metric_system"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:39:48.437355+00:00"
instance: "kb-cron"
---

==== Quadrant–eleventhgram–second (QES) or International System of Electrical and Magnetic Units ====
The CGS units of measure used in scientific work were not practical for engineering, leading to the development of a more applicable system of electric units especially for telegraphy. The unit of length was 107 m (the hebdometre, nominally the Earth quadrant), the unit of mass was an unnamed unit equal to 10−11 g and the unit of time was the second. The units of mass and length were scaled incongruously to yield more consistent and usable electric units in terms of mechanical measures. Informally called the "practical" system, it was properly termed the quadrant–eleventhgram–second (QES) system of units according to convention.
The definitions of electrical units incorporated the magnetic constant like the EMU system, and the names of the units were carried over from that system, but scaled according to the defined mechanical units. The system was formalised as the International system late in the 19th century and its units later designated the "international ampere", "international volt", etc.

==== Heaviside–Lorentz system of units ====
The factor 
  
    
      
        4
        π
      
    
    {\displaystyle 4\pi }
  
 that occurs in Maxwell's equations in the gaussian system (and the other CGS systems) comes from the 
  
    
      
        4
        π
      
    
    {\displaystyle 4\pi }
  
 steradians surrounding a point, such as a point electric charge. This factor could be eliminated from contexts that do not involve spherical coordinates by incorporating the factor into the definitions of the quantities involved. The system was proposed by Oliver Heaviside in 1883 and is also known as the "rationalised Gaussian system of units". The SI later adopted rationalised units based on Heaviside's rationalisation scheme.

=== Thermodynamics ===
Maxwell and Boltzmann had produced theories describing the interrelationship of temperature, pressure, and volume of a gas on a microscopic scale but otherwise, in 1900, there was no understanding of the microscopic nature of temperature.
By the end of the nineteenth century, the fundamental macroscopic laws of thermodynamics had been formulated and, although techniques existed to measure temperature using empirical techniques, the scientific understanding of the nature of temperature was minimal.

== Convention of the metre ==

With increasing international adoption of the metre, the shortcomings of the mètre des Archives as a standard became ever more apparent. Countries which adopted the metre as a legal measure purchased standard metre bars that were intended to be equal in length to the mètre des Archives, but there was no systematic way of ensuring that the countries were actually working to the same standard. The meridional definition, which had been intended to ensure international reproducibility, quickly proved so impractical that it was all but abandoned in favour of the artefact standards, but the mètre des Archives (and most of its copies) were "end standards": such standards (bars which are exactly one metre in length) are prone to wear with use, and different standard bars could be expected to wear at different rates.
In 1867, it was proposed that a new international standard metre be created, and the length was taken to be that of the mètre des Archives "in the state in which it shall be found". The International Conference on Geodesy in 1867 called for the creation of a new international prototype of the metre and of a system by which national standards could be compared with it. The international prototype would also be a "line standard", that is the metre was defined as the distance between two lines marked on the bar, so avoiding the wear problems of end standards. The French government gave practical support to the creation of an International Metre Commission, which met in Paris in 1870 and again in 1872 with the participation of about thirty countries.
On 20 May 1875, an international treaty known as the Convention du Mètre (Metre Convention) was signed by 17 states. This treaty established the following organisations to conduct international activities relating to a uniform system for measurements: