Letter, from Charles Wheatstone to Sir John Herschel, dated at 20 Conduit St, London Autograph letter signed by sender. Accepts John Frederick William Herschel's invitation to demonstrate [on 28 Aug.] Charles Wheatstone's portable optical and acoustical experiments and the 'whirling machine.' Asks John Frederick William Herschel to supply 'an electrical machine and a good sized jar.' Encloses copy of Charles Wheatstone's paper on Jew's harp. Will bring another paper and new 'Symphonion' for Mary Herschel. 23 August 1833