Magnetic variation observations at Lemon Valley, St. Helena, [South Atlantic Ocean], by Henry Foster and others Daily magnetic observations, in three columns, recording hourly position of the north end of the dip needle [degrees, minutes, seconds] at appointed observation times, with temperature in Fahrenheit. With a title page: 'Horary Variation of the Magnetic Needle Lemon Valley St. Helena'. Each page is headed: 'Increasing Readings denote North end going to the Eastward. Observations on the Diurnal Variation of the Magnetic Needle, at Lemon Valley St. Helena'. 8-28 January 1830