Letter, from John Tyndall to Sir John Herschel, dated at [Royal Institution] Autograph letter signed by sender. Apologizes for not having seen John Frederick William Herschel's paper on spectra of colored flames and thus having overlooked John Frederick William Herschel's prior claims [see John Frederick William Herschel's 1861-7-21]. Will try to make amends. 24 July 1861