DELAMBRE, Jean-Baptiste-Joseph & MÉCHAIN, Pierre-François-André. Base du système métrique décimal, ou mesure de l’arc du méridien compris entre les parallèles de Dunkerque et Barcelone, exécutée en 1792 et années suivantes

DELAMBRE, Jean-Baptiste-Joseph & MÉCHAIN, Pierre-François-André.

Quarto (252 x 195 mm.), 3 volumes, [2] leaves, 180 pages [II], 551 pages with 8 plates; XXIV, 844 pages with 11 plates; [2] leaves, 704, 62 pages with 9 plates. A very fine set bound in slightly later half calf, spines gilt.

First edition, rare. ‘For many centuries there were no general standards for measurement: every trade and craft had its own peculiar units and they differed even in various regions of the same country. Since the development of international trade in the Middle Ages this chaotic situation had become more and more tiresome, but all efforts towards standardization were strongly resisted by vested interest. […] We owe the introduction of an international metric system to the French Revolution. In 1790 the Académie des Sciences, at the request of Talleyrand, set up a commission to consider the question: among its members were J. C. Borda, Lagrange, Laplace, G. Monge and Condorcet. In 1791 they reported that the fundamental unit of length should be derived from a dimension of the earth: it should be the ten-millionth part of a quadrant of the earth’s meridian extending between Dunkirk and Barcelona. As the distance was already approximately known, a provisional meter was at once adopted. The new unit of weight was to be the gram: the weight of one cubic centimeter of water at 4° C. The Constituent Assembly set up a general commission of weights and measures to carry these proposals into effect and in 1795 a law was passed introducing the metric system into France with provisional standards. The astronomers Jean Baptiste Joseph Delambre and Pierre Francois André Mechain were charged with the task of measuring accurately the newly adopted length along the meridian arc between Dunkirk and Barcelona. Owing to the disturbances of the revolutionary period their work was much impeded, but in 1799 their measurement was completed. The above work - Base du système métrique décimal – embodies their report. The length of a meter (equaling 39.37 English inches) was marked on a platinum bar, and the unit of weight was also constructed of platinum, being the weight of a cubic decimeter, or liter, of pure water at its maximum density. These original bars remained the basic standards until 1875 and are still preserved in Paris. The metric system was gradually accepted by most nations – with the notable exceptions of England and (for weights and measures) the United States; but optional use was legalized in 1864 (England) and 1866 (U. S. A.) and its general adoption in England was proposed in 1965. After meetings of an international commission in 1872 the International Bureau of Weights and Measures was set up in 1875. It is now situated near Sèvres and has since remained the international center for all questions of standards. New units made from a bar of platinum alloyed with 10 per cent iridium were constructed, copies of which were distributed to the various participating countries.’ (PMM)

PMM 260; Norman 1481; En Francais dans le Texte 212.