The historical French heritage

France is very rich in systematic observations of coastal sea level over long time periods. The oldest (published) series of measurements were performed by the astronomers La Hire and Picard at Brest, France, in 1679, over about ten days. They repeated the experiment in 1692, over several months, again in Brest. Their aim was to study the tides and their results showed the fundamental importance of observation to understand and determine the characteristics of tides in a given place for the purposes of prediction. As early as 1700, sea level observatories sprung up along the coast of France with the help in particular of the Académie des Sciences. The invention of an automatic mechanical recording device is attributed to Henry Palmer in 1831. In France, the French hydrographic engineer R. Chazallon (1802-1872) devised a mechanical instrument in the 1840s (1st installation in 1843 in Algiers), giving it the name of marégraphe. The geographical engineers also distinguished themselves in this field, particularly with the invention of the medimarametre at the end of the 19th century by Ch. Lallemand (1857-1938), and the development of a method to test the accuracy of mechanical tide gauges by C. van de Casteele (1903-1977), a method which bears his name in volume I of the Manual on sea level measurements and interpretation, Unesco (IOC 1985).