Asks THH question on flow of glaciers after ice has been fractured and fragmented.

CD had to leave Royal Society lecture [joint paper by THH and J. Tyndall, "On the structure and motions of glaciers", Philos. Trans. R. Soc. Lond. 147 (1857): 327–46] before the end because of headache.

THH comments on G. A. Brullé’s paper ["Researches upon the transformations of the appendages of the Articulata", Ann. & Mag. Nat. Hist. 13 (1844): 484–6].

On classification and possibilities of a scientific morphology and zoology. CD’s "pedigree business" is important for physiology but has nothing to do with pure zoology any more than human pedigree has to do with the census. Zoological classification is a census of the animal world.

THH’s catalogue [THH and R. Etheridge, A catalogue of the collection of fossils in the Museum of Practical Geology (1865), part published in 1857] best résumé he has seen of science of natural history. On classification he is not quite sure that he wholly goes along with THH. Encloses a few criticisms of THH’s preface.[enclosure survives as copy only].