Letter, from Thomas Young to Sir John Herschel, dated at 48 Welbeck St. Autograph letter signed by sender. Asks John Frederick William Herschel to check accuracy of Nautical Almanac entry for Jupiter's satellites III and IV on 20 Aug. 1819. Thanks for John Frederick William Herschel's note, but tell James South 'he is bound to give his reasons....' 1822-4