Letter, from Sir Charles Lyell to Sir John Herschel, dated at 16 Hart St. Autograph letter signed by sender. Has been requested by Gideon Mantell to write John Frederick William Herschel a letter of introduction for a Lieut. H. I. Thomas, a friend of Davies Gilbert. Thomas wishes to be the bearer of any letter or parcel CL may have. Believes that a copy of the President's speech he sent may be lost in the post. Thinks that John Frederick William Herschel's theory of subterranean isothermal lines interesting. Dined with the Somervilles last Sunday. 31 January 1837