Reports two observations on crossing in dogs: the preservation of both pure types in the offspring of a pointer and a setter, and the influence of a first mating with a mongrel on the progeny of a Barbary bitch and a subsequent Barbary male.

Sends corrected title of Variation and report of progress in printing.

WSD is pleased that CD approves his index draft [for Variation]; notes his objection to long list of references under "Dogs" and will try to find a principle for shortening it. He has not indexed all authors’ names; is this practice satisfactory?

Provides JH with best definition that GA has available for the gallon [see JH's 1867-11-3], noting that methods for establishing standards are revised, even if the standards supposedly are not.

Plans for refracting telescope TW is constructing. Diagrams and questions about lens construction.