GEOMAGNETISM AT THE ROYAL-OBSERVATORY, GREENWICH

The Royal Observatory at Greenwich was founded for the improvement of navigation at sea. It was natural, therefore, that the study of declin ation and magnetic charting should become part of its remit. Sporadic observations were followed by a more continuous series, but it was not until Greenwich joined the Gottingen Magnetic Union that the regular observation of elements other than D was started. At first these were simply of variations on 'term-days', but with the introduction of abso lute instruments and of photographic recording it soon became a full-b lown magnetic observatory. This flourished, albeit with site and instr umental changes, until 1926 when interference from electric railways p olluted the site and a move was made to Abinger. Magnetic cartography continued at Greenwich, together with spherical and spheroidal harmoni c analyses, and the production of an observatory yearbook which was ta ken as a model for the world. During the war valuable work was done on the de-gaussing of ships. The staff has included such magnetic lumina ries as Edmond Halley, George Airy, James Glaisher, Harold Spencer Jon es and Sydney Chapman.