network. Following the example set by this country and under the patronage of the International Geodetic Association, Austria, Bavaria, Prussia, Russia and Saxony undertook gravity determinations on their respective territories. As the figure of the Earth could be inferred from variations of the seconds pendulum length with latitudes, the United States Coast Survey's direction instructed Charles Sanders Peirce in the spring of 1875 to proceed to Europe for the purpose of making pendulum experiments to chief initial stations for operations of this sort, in order to bring the determinations of the forces of gravity in America into communication with those of other parts of the world; and also for the purpose of making a careful study of the methods of pursuing these researches in the different countries of Europe. In 1886 the association changed name for the International Geodetic Association (German: Internationale Erdmessung). After the death of Johann Jacob Baeyer, Carlos Ibáñez e Ibáñez de Ibero became the first president of the International Geodetic Association from 1887 to his death in 1891. During this period the International Geodetic Association gained worldwide importance with the joining of United States, Mexico, Chile, Argentina and Japan. Efforts to supplement the various national surveying systems, which began in the 19th century with the foundation of the Mitteleuropäische Gradmessung, resulted in a series of global ellipsoids of the Earth (e.g., Helmert 1906, Hayford 1910/1924) which would later lead to develop the World Geodetic System. Nowadays the practical realisation of the metre is possible everywhere thanks to the atomic clocks embedded in GPS satellites. International prototype metre The intimate relationships that necessarily existed between metrology and geodesy explain that the International Association of Geodesy, founded to combine and use the geodetic works of different countries, in order to reach a new and more exact determination of the shape and dimensions of the Globe, gave birth to the idea of reforming the foundations of the metric system, while expanding it and making it international. Not, as it was mistakenly assumed for a certain time, that the Association had the unscientific thought of modifying the length of the metre, in order to conform exactly to its historical definition according to the new values that would be found for the terrestrial meridian. But, busy combining the arcs measured in the different countries and connecting the neighbouring triangulations, geodesists encountered, as one of the main difficulties, the unfortunate uncertainty which