Notebook of horizontal force magnetometer observations made at Colaba Observatory, Bombay [Mumbai], India, by [Arthur Bedford Orlebar] Daily readings of horizontal changes to the Earth's magnetic field. Columns for time, [observed] reading, [middle] doubled, sum, mean, thermometer and remarks. The notes are bound within a paper cover, inscribed: '1st April 1842. Horizontal Force' [multiple times]. The rear cover is similarly inscribed, but with the names 'John H. Taub' and 'Bernard Fetherston'. 1-23 April 1842