The geophysical observatory of Chambon‐la‐Forêt

Abstract

The development of electric‐railway lines, particularly in the vicinity of large cities, has made necessary in recent years the transfer of several magnetic observatories to more isolated and magnetically undisturbed sites. Thus in the last decade it has been found necessary to move the principal magnetic observatory of Germany from Seddin to a new site at Niemegk and the Sverdlovsk (formerly Ekaterinburg) Observatory, where for nearly 100 years magnetic observations had been in progress, to Vyssokaja Dubrava, some 30 km from the old location.We now learn from a booklet kindly furnished us by Professor Ch. Maurain, that the central magnetic observatory of France, previously located at Val‐Joyeux, about 25 km from Paris, owing to the encroachment of industrial electric currents, has been moved to a clearing in the Forest of Orléans, Commune de Chambon‐la‐Forêt (Département du Loiret), 87 km south of Paris. The geographical coordinates of the new observatory are latitude 48° 01′ 26″ north, longitude 2° 15′ 36′′ east of Greenwich, or 0° 04′ 38″ west of Paris; the elevation above sea‐level of the pier where the magnetic observations are made is about 133 meters. The greater part of the site lies in a clearing in the forest, the remainder being wooded. A determination of the magnetic susceptibility of several samples of the soil gave a mean value of 2×10−6, so that the soil may be regarded as practically non‐magnetic.