Happy to be reunited with mother. JH thanks CH for his enjoyable stay in Hanover. Wishes CH well on her [catalogue of] nebulae.

Decides not to go to Switzerland because he wants to visit Hanover. On the way, hopes to see Johann Pfaff at Erlangen, Johann Encke at Seeburg, Baron Bernhard von Lindenau at Gotha, and Carl Gauss and Karl Harding at Göttingen among others.

Describes his laborious journey to the summit of Mt. Etna; from his barometric readings, concludes that its altitude is 10,000 or 11,000 ft. Asks about the progress of Johann Pfaff's translation of William Herschel's papers; JH mentions that he wrote to Pfaff from Cattagione, Sicily. [Letter continued 20 July from Naples and 16 Aug. from Florence.]

Regarding the First Assistant at Greenwich Observatory, and the possibility of JH ever becoming Astronomer Royal. Hopes to see him on Wednesday.

Relates experiences and persons met recently in Paris. Account of Alpine scenery and travel experiences. [Continued 1824-4-20 Turin:] Events while travelling to Turin. [Continued 1824-4-22 Alessandria:] Has met Plana at Turin Observatory. Five days of discussions with him. Please order two specified books and send to Plana. View of the Alps.

Recent experiences in crossing the Alps. Overturning of the coach and his narrow escape.

Recent meeting and astronomical observations with G. B. Amici. [Repeat of his narrow escape in the Alps, related in JH's 1824-5-5]

Is observing the heavens from Etna. [Letter continued 11 July from Palermo:] Recent experiences touring Sicily.

His recent tours in Italy and Germany, and the people he met.

Praises old Edinburgh Philosophical Journal. Promises to send DB some materials for publication.

Mislaid the copy of one of JB's mss. and would be grateful if he knows of its whereabouts. In the course of his travels in Europe he has seen some astronomical instruments, which will in time surpass any British made ones and especially those of G. B. Amici and Josef Fraunhofer.

Sends GA information about indices of refraction in different glasses and in different parts of the spectrum; also recommends the writings of Josef Fraunhofer.

Observations of Venus by William Herschel and JH. Only J. H. Schröter claims to have seen 'deep marginal indentations' that JP claims.

Thanks TY for books and for taking charge of [G. A. A.] Plana's plates. JH mentioned Eilhard Mitscherlich only when no other proposals came forth. Matter was left hanging. Assures TY that JH was not offended [see TY's 1824-11-21, i.e., #1075]. Regrets 'dilapidated state of scientific matters' in R.S.L.

Acknowledges letters from AB and French Board of Longitude received by Astronomical Society. Thanks for care given to JH's reflecting theodolite by Mr. Schenk. Promises copy of JH's and James South's [1824] article on double stars. Hopes to hear from J. B. Fourier regarding biography of William Herschel.

JH's theory of colors. Edward Troughton has DB's instrument one-third completed. When will DB want JH's encyclopedia article on 'Variation'?

Henry Kater's triangulation survey of north Scotland. Edward Sabine's study of pendulum lengths at various latitudes. François Arago did not receive letters from JH and Francis Baily. Comments on rumor of [Isaac] Newton's madness. JH plans to reduce transit observations of fixed stars at Greenwich since [James] Bradley's time. Are French and other astronomers in agreement on common system of reductions? Will visit Paris next month. Observed curious phenomena in voltaic electricity.

Receipt and shipment of various papers and letters. Robert Molyneux has not received payment for clock. JH ordered another for L. A. Fallon; it is ready to ship. Clarifies Edward Sabine's remark about pendulums. Hopes to translate JL's Analytical Geometry. JH translated JL's 'empirical formula of refraction.' Believes JL's method of determining latitude without knowing the time is not new. Notes J. W. A. Pfaff's translation of William Herschel's works.

Orders missing issues of Astronomische Nachrichten. Answers HS's question about JH's essay on Physical Astronomy. James South's testimony 'vindicated' Josef Fraunhofer's repeating micrometer to Edward Troughton. C. F. Gauss's mode of determining powers of telescopes. Nothing heard of Captain [Maughan?]. Directions for sending [K. L.] 'Harding's atlas' to JH. Gives J. F. Daniell's address. Astronomical Society is gratified that HS dedicated book to it. Shall direct Robert Molyneux to send L. A. Fallon's clock to HS.

If JS has not already passed on to Humphry Davy JH's letter of 1823-12-21, JS should do so immediately. If post of Astronomer Royal should become vacant, JH would be interested in it, but would not wish to work with Stephen Lee, then under consideration for appointment as head assistant at Greenwich.