Letter, from William Henry Smyth to Sir John Herschel, dated at [3 Cheyne Walk, Chelsea] Autograph letter signed by sender. Sends correction to data for Gamma Virginis. Asks if John Frederick William Herschel has 'considered the puzzle of Aristarchus [lunar crater]' discussed in William Henry Smyth's Cycle of Celestial Objects. 30 April 1845