Letter, from George W. Hearn to Sir John Herschel, dated at Royal Military College, Sandhurst Autograph letter signed by sender. Has been investigating the Cavendish experiments recently repeated by Francis Baily. Thinks G. B. Airy has neglected the resistance of the air in his mathematical theory. Would like to send an abstract of his investigations so that John Frederick William Herschel can judge their merits. 6 January 1847