Magnetic variation observations at Point St. Francisco, Maranham [Maranhao, Brazil], 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 a Magnetic Needle Point St. Franciso Maranham'. Each page is headed: 'Observations on the Horary Changes of a Magnetic Needle, at Maranham'. 3-24 August 1830