Letter, from John Henry Dallmeyer to Sir John Herschel, dated at 19 Bloomsbury St. Autograph letter signed by sender. Has made a trial of John Frederick William Herschel's lens but it was too large to be satisfactory. Regarding the 'graphoscope,' a new toy. Has been concerned with the manufacture of an improved form of opera glass. Present forms have many imperfections. Gives details of his own theories and sends one for John Frederick William Herschel's notice. 23 December 1870