Letter, from James Prinsep to Sir John Herschel, dated at Calcutta Autograph letter signed by sender. Thanks John Frederick William Herschel for meteorological observations and tells how he will apply them to predictions for Calcutta. Describes need to correct barometer observations. Compiles and compares barometer reading from points of India and Central Asia. Thanks John Frederick William Herschel for double star observations, which he sends to Madras Observatory. 19 June 1836