compare the geodetic standards of length used in the different countries. The British Government invited those of France, Belgium, Prussia, Russia, India, Australia, Austria, Spain, United States and Cape of Good Hope to send their standards to the Ordnance Survey office in Southampton. Notably the geodetic standards of France, Spain and United States were based on the metric system, whereas those of Prussia, Belgium and Russia where calibrated against the toise, of which the oldest physical representative was the Toise of Peru. The Toise of Peru had been constructed in 1735 as the standard of reference in the Spanish-French Geodesic Mission, conducted in actual Ecuador from 1735 to 1744. In 1861 Johann Jacob Baeyer published a report suggesting that European countries should cooperate in the determination of the figure of the Earth. In 1862, when Denmark, Saxe-Gotha, the Netherlands, Russia (for Poland), Switzerland, Baden, Saxony, Italy, Austria, Sweden, Norway, Bavaria, Mecklenburg, Hanover and Belgium decided to participate, Bessel's Toise was adopted as international geodetic standard. As a forerunner in Europe, Spain adopted the metre as geodetic standard. In 1866 Spain joined the geodetic association and was represented by Carlos Ibáñez e Ibáñez de Ibero. He had devised a geodetic standard calibrated against the metre which had been compared to the Toise of Borda (a copy of the Toise of Peru constructed for the measurement of the Paris meridian arc by Delambre and Mechain), which served as a comparison module for the measurement of all geodesic bases in France. A copy of the Spanish metric geodetic standard was made for Egypt. In 1863, Ibáñez and Ismail Effendi Mustafa compared the Spanish Standard with the Egyptian Standard in Madrid. These comparisons were essential, because of the expansibility of solid materials with raise in temperature which had been demonstrated during the 18th century. The famous French physicist and geodesist Pierre Bouguer had exhibited its effect to a large assembly at the Hotel des Invalides. Indeed, one fact had constantly dominated all the fluctuations of ideas on the measurement of geodesic bases: it was the constant concern to accurately assess the temperature of standards in the field; and the determination of this variable, on which depended the length of the instrument of measurement, had always been considered by geodesists as so difficult and so important that one could almost say that the history of measuring instruments is almost identical with that of the precautions