| Description | Written from the Royal Observatory, Greenwich, London. The letter apologises for not having replied to Brunel previously and discusses the results of various experiments that Airy has been running with existing astronomical instruments, some of which have been remarkably unsuccessful. The letter also offers Airy's suggestions on the theoretical construction of such instruments and offers various points of advice about the possibility of creating a suitable instrument for observing an artificial horizon at sea and holding the instrument steady in a rolling sea. There is a sketch of a possible instrument at the bottom of Folio 57. |