Thanks CL for the gift of a new edition of CL's Principles of Geology. JH comments on a number of issues, in a very long letter, including the replacement of extinct species by other species, CL's solution of the problem of the variation of climate, and the evolution of language. JH speculates at length on the isothermal activity under the earth's crust that may result in volcanoes or the formation of new land masses, and describes a considerable number of geological examples that JH sees as supporting CL's ideas.