Plate, curves of diurnal change in magnitude and direction 1841-1847 by [George Biddell Airy] Plate XVI showing diagrams of curves representing the diurnal change in magnitude and direction of magnetic forces in the horizontal plane acting on the north end of the needle at the Royal Observatory in Greenwich from 1841-1847. Subject: Geodesy Published in Philosophical Transactions as 'On the diurnal inequalities of terrestrial magnetism, as deduced from observations made at the Royal Observatory, Greenwich, from 1841 to 1857'. Written by Airy at the Royal Observatory, Greenwich. Received by the Royal Society on 8 April 1863. Read 23 April 1863. [1863]