Writes to correct error JH identified in GP's memoir [see GP's 1826-1-18]. Also asks to have two additional passages added to improve memoir. Intends to come to England next winter. Is including a list of corrections for the memoir [list is missing].

Has received a package of books from JH, some of which will be sent on as instructed. Is interested in the work of JH and James South on double stars. Also comments on parallax measure of the sun and on transits of Venus. Wants to respond to P. S. Laplace's theory of Jupiter and Saturn.

Is sending JH some of GP's work, some of it to be forwarded. Refers to a note by GP in some of F. X. von Zach's writings, which GP would like to have added to his memoir being published by the Astronomical Society. GP comments on the status of some of his own astronomical projects.

Still concerned about possible changes to GP's memoir [see GP's 1826-1-28] due to the work of P. S. Laplace. Comments on illness [?] of F. X. von Zach.

Thanks HO for JH's election to the Royal Academy of Copenhagen. Comments on some chemical and magnetical experiments.

Chemical constitution of meteorites. JH suspects lead-iron alloy. Believes this has not been proposed before. Send specimen for JH's analysis.

JH plans to explore volcanic districts of Auvergne and Vivarais, then along Rhine to Bonne and Andermatte. Has cancelled plan to cross to Staffa [Scotland] and explore there.

Asks JH about Dr. Balfour's account in Asiatic Researches about lunar effects on humans in India.

Comments on Josef Fraunhofer's work on double stars, on quality and color of light from different sources, refraction of different kinds of light, and solution of a problem in conic sections. Is going to Geneva and Modena soon.

Describes observations made as he travelled and people visited on journey from London to Ancona.

Talks about Josef Fraunhofer's failing health and his making of flint glass.

Is sending on two items directed to JH through WT.

Returns house keys. Smooth passage across Channel. Met James Grahame's brother-in-law, Mr. Robison, who is going to Paris to be married. James South arranged carriage for JH's travels in France. Servant James Child is well and observed four criminals executed in London before departing. News of Beckwiths.

Journey from London and French countryside. Towns and Paris are vastly improved since 1801 visit. Charles Babbage and wife are in Paris. Received letters of introduction from Georges Cuvier, J. N. Nicollet, and J. P. Delessert for JH's expedition to Auvergne. Alexis Bouvard is recovering from fall. Georgianna Babbage has recovered and promised to write to MPH. [Letter continued 4 Sept. in Moulins:] Traveled more than 100 miles today. [Letter continued 5 Sept. in Clermont-Ferrand:] Massive flooding in Riom. Impressive view of volcanoes. [Letter continued 6 Sept.:] Will ascend Puy de Dôme today with two companions.

Two unwanted companions caused JH to waste two days in Clermont-Ferrand. Describes volcanoes and high winds on peaks. Actinometer experiments on Puy de Dôme. Hunting fossil bones of extinct animals.

Describes region around St. Flour, where servant James Child was seriously ill for two days. Low opinion of French physicians. Journey to Montpellier.

Tour delayed at least one week. Clouds have restricted JH's actinometer experiments on mountains. Describes active volcano and vineyards near Agde. Ancient ruins in Nismes [Nîmes].

Death of James Grahame's relative. Explored volcanoes in Vivarais Mountains. Describes Mont Blanc at sunset. Regrets bypassing St. Bernard. Expects to reach London by 13 Oct.

Plans leisure sightseeing in Paris. Visited Louvre. [P.S. 7 Oct.:] Called on Alexis Bouvard yesterday. Met W. H. Wollaston, returning from Tyrol. Wrote to Caroline Herschel from Montpellier. Will view A. M. Ampère's electrical experiments today.

Questions and comments regarding improvements in microscopy.