Preparing fifth edition of Principles of Geology, using JH's facts about boiling seeds. Mathematical error in CL's climate theory. CL's first speech as president of Geological Society. Criticizes R.S.L. JH's volcanic theory was too complex; will incorporate it into later editions. Benefits to science of Charles Babbage's social parties. Latest publications in geology. P.S. Glad to learn that JH thinks origin of new species may occur through intermediate causes; Germans criticized this. CL chooses not to engage in controversies. Speculates on successive extinction of species. Notes on African hot springs.

Charles Lyell wrote letter to JH recently. Now encloses with it letters of introduction to persons in Rio and abstract of paper by Charles Babbage. [Henry] Brougham's attacks on Thomas Young.

Comments on [MS of] CD’s paper ["Elevation on the coast of Chili" (4 Jan 1837), Collected papers 1: 41–3].

Invites CD to dinner. "Don’t accept any official scientific place, if you can avoid it".