Discusses Louis Agassiz’s theory of the glaciation of Brazil.

Discussion of Mrs Agassiz’s letter [to Mary Lyell, forwarded to CD] regarding S. American glacial action,

with comments on Bunbury’s letter on temperate plants.

Refers to opinions of Agassiz, David Forbes, Hooker, and CD on glacial period and glaciers.

Wishes he had published a long chapter on glacial period [Natural selection, pp. 535–66] written ten years ago.

Tells of death of his sister, Catherine, and other family matters.

Thanks CL for Hooker’s letter.

Discussion of Hooker’s views on glacial action and temperature with specific reference to S. America.

His squabbles with Hooker on transport of seeds via water currents,

temperate plants, and preservation of tropical plants during cooler period.

Expresses interest in seeing Agassiz’s letter.

Discusses CD’s and J. D. Hooker’s letters to Lyell concerning Louis Agassiz’s theory of the glaciation of the Amazon basin in Brazil.

Comments on errors [in Origin] pointed out in C. J. F. Bunbury’s letters.

Mentions CD’s notes on Drimys, Fuchsia, and fossil mammals of Brazilian caves.

Sorrowful that his work must be put aside because Murray wants a new [4th] edition of Origin. Remarks on changes to be made regarding Organ Mountains and Agassiz’s glacial markings.

Feels sure that at times the globe must have been superficially cooler. Believes CD will turn out right with regard to migration across the equator via mountain chains, while the tropical heat of certain lowlands was retained.

Has returned memorial to Chancellor of Exchequer; thanks CL for his note.

Lengthy remarks on cool period. Did not know of CL’s interest. New facts in new German and English [4th] editions of Origin will be too late for CL’s use. CD’s ten-year-old MS on cool period is available.

Surprised at Hooker’s introducing "so organic a change as a deviation in the axis of the planet" to explain the cold of the Glacial Period.

Gives details of enclosed MS on cool period. Mentions Hooker’s opposed "axis of the earth" view. Causes of glacial period are beyond CD; "cannot believe change in land and water being more than a subsidiary agent".

Comments on cool-period MS. Still believes geographical changes principal cause of former changes of climate.

Disappointed to put off CL’s visit because of illness of CD’s sister [Susan], but hopes to see him in October.

Thanks for lending pamphlet [L. Agassiz, Geology of the Amazons]. Agassiz has written "wild nonsense".

Refers to a translation of Pictet and Humbert’s "capital" paper on fossil fish ["Recent researches on the fossil fishes of Mount Lebanon", Ann. & Mag. Nat. Hist. 3d ser. 18 (1866): 237].

Hooker’s lecture at BAAS Nottingham meeting.

Hopes to send a copy of his new edition [of Principles of Geology] in a few weeks. Hopes he will be satisfied with the manner in which he used JH's drawings. Comments about variations in the obliquity of the ecliptic. Quotes correspondence he has had with E. J. Stone of Greenwich Observatory. Would like JH's opinion on the matter.

Comments on the relationship between the plane of the earth's orbit and the obliquity of the ecliptic.

Comments on proofs [of Principles of geology, 10th ed. (1867–8)]: CL does not allude to the specialisation of classes.

Discusses CL’s argument from the absence of Cetacea in Secondary rocks;

finds his discussion of man "superfluous and too orthodox".

More comments on proofs [of CL’s Principles of geology, 10th ed.]. Discusses permanence of continents and other points.

Refers to passage describing evaporation of snow in Journal [of researches, pp. 277–8].

Cites astronomers’ views on increasing length of day.

Comments on some of CL's writings; further argues that a canal at Suez and/or Darien would have a major effect on European climate due to the effect of ocean currents coming through such canals.

Did not intend to trouble him with his proofs, but as he has cited JH in the chapter dealing with the astronomical effect on climate he sends proofs for this chapter. Would like to quote JH's two letters on the subject. The whole book is set up and hopes to send the volume in November.

Some minor suggestions regarding CL's proofs [see CL's 1866-10-19].

Was pleased to get his twelve pages of slips returned this morning. In one he proposes an alteration of 3% instead of 1003 to 1000. Which is correct?

CD asks if he can call tomorrow (Friday) at 9: 30, and offers to come on Saturday if that would suit CL better.