Plate, 'March 1825' by Henry Foster Chart showing magnetic needle variation at Port Bowen in March 1825, with some annotations indicating time of day. A graphite annotation on verso of this plate erroneously reads 'Phil Trans. Plates 1836'. Subject: Magnetism / Navigation Published in Philosophical Transactions as 'Observations on the diurnal changes in the position of the horizontal needle, under a reduced directive power, at Port Bowen, 1825'. Communicated 12 January 1826. March 1825