He and Emma rejoice that GHD’s mathematical troubles are at an end. It is miraculous that he unconsciously followed the right course – like composing a sonata by a fluke.

Recounts the experiments on Fechner’s law he has found in Helmholz; they are on the smallest perceptible differences of illumination. Describes how to test whether plants’ responses to lights are in accordance with it.

Rejoices that he should have "staggered" William Thomson so quickly and that the latter should speak of GHD’s "discovery". The internal heat [of the earth] will please geologists and evolutionists.

Forwards pamphlet (Jules Carret 1878) to GHD.

Encloses William Thomson’s report on GHD’s paper. Some of it was written in Rayleigh’s hand.

Delighted with [William Thomson’s] report. "There can be no doubt now about the value of your work." CD has "not been so much pleased for a long time".

Asks CD if he would screw himself up to inviting A. Newton to Down.

Thanks CD [for his increased allowance?].

Writes of his tour [in Algeria].

Fears he cannot give much information for CD’s book [Erasmus Darwin]. Recounts how his mother’s health was improved by Erasmus Darwin’s treatment. Remembers being attacked as a boy by an angry lady whose beautiful teeth were extracted by Dr Darwin "to cure some nervous spasms".

Thanks him for his efforts. CD cared most about the letter to Thomas Okes [see Erasmus Darwin, pp. 14–15]. "Cannot think who the calumnious article cd have been about [in?] 1802."

Has no letters or papers [of Erasmus Darwin].

Suggests CD cite some of Erasmus Darwin’s poems to answer the charge of atheism [see Erasmus Darwin, p. 44].

Recounts a story of a remarkable cure by Dr Darwin, showing his sagacity and daring.

Thinks King’s College Library may have the letters of his grandfather [Thomas Okes of Exeter]. [See Erasmus Darwin, p. 14.]

Encloses some references [missing] to information on Dr Erasmus Darwin.

Asks GHD to look in Cambridge University Library for Monthly Magazine articles containing a malicious calumny concerning Dr [Erasmus] D[arwin] [see Erasmus Darwin, pp. 65–70].

Asks GHD to look for a life of Sir Henry Rayburn [Raeburn] "who is spoken of as famous and who painted Charles Darwin [1758–1778] when dead". Asks why he painted the corpse.

Sends CD an article on Dr Erasmus Darwin [from Monthly Magazine, see 12028].

Tells of a "discovery" he has made about taking observations of the sun. Does not know yet whether it is new.

A big book arrived for GHD before CD left Down. Hopes it is Thomson and Tait [Treatise on natural philosophy, 2 vols., 2d ed. (1869)]. It shows what they think of GHD.

Thinks it grand if GHD has made a correction about "such an old sinner as the Sun" and hopes his arithmetic on his old subject will turn out right.

Sends abstracts of more articles [on Dr Erasmus Darwin] from Monthly Magazine.

CD is particularly obliged for the copy of Maria Edgeworth’s letter.

Sends some queries connected with his writing of the biographical preface to Erasmus Darwin.