Letter, from Charles Wheatstone to Sir John Herschel, dated at Swan Inn, Windsor Autograph letter signed by sender, with annotations by recipient. Appreciates John Frederick William Herschel's interest in and encouragement of Charles Wheatstone's experiments. Describes new experiments to elucidate theory of undulatory motion of sound and light. Invented 'kaleidophone' to display paths of vibrating rods. Hopes John Frederick William Herschel can confirm these results. 23 August 1825