Thanks SW for a copy of the reviews of JH's Meteorology and Physical Geography. Comments on related matters such as importing English birds into Australia, observations made by Alexander von Humboldt, and catching specimens behind a sailing ship.

Due to poor health of both JH and his wife, Margaret, JH writes to decline an invitation to dinner.

Thanks for sending vol. 4 of BP's Infinitesimal Calculus and for earlier sending vols. 1 and 2. Praises parts of vol. 4. Will another volume be forthcoming?

Describes objections to proposed metallic thermometer. Describes another simpler design for a metallic thermometer. Will ask [William] Sykes to consider HR's design.

Has been too ill to write terrestrial magnetism paper for Edinburgh Review. Suggests other people to write it.

Has signed certificate for [W. F.] Hook. [See ES 1861-12-5] Congratulates ES [on presidency of R.S.L.]. JH on B.A.A.S. balloon committee. Proposes design for metallic thermometer.

Pleased ES and [Balfour?] Stewart like plan for metallic thermometer. Suggests way to obviate effect of pendulous movement of the suspended weight.

Advises on the construction of the Melbourne reflecting telescope. Thinks [W. P.] Wilson should come to watch construction.

Has no suggestions to improve photographs. Wants to determine whether the degradation of light from center to edge of sun is 'real.' Does not think sun's size affects focus.

Thanks MS for sympathy letter. Discusses present situation in Italy. Discusses his children and their scattered locations, e.g., a son fighting in the Indigo affair. Discusses his articles for Encyclopaedia Britannica.

Finds JT's work on thermotics 'highly interesting,' although criticizes measurements of 'tenuity' of vapor, and explanation of scattering of sunlight and formation of corona around moon during eclipse.

Discusses the project of erecting a large telescope in the southern hemisphere [Melbourne telescope] for observation of nebulae. Expresses reservations and makes suggestions about the project.

Reply to JT's 'Remarks on Radiation and Absorption.' Calls non-absorption of air and vapor key to understanding meteorological phenomena. Remarks on 'radiant heat' from moon.

Stresses importance for Balloon Committee of obtaining corresponding temperatures and pressures; describes two highly sensitive thermometers that might be built for this purpose.

Thanks for MS's works, communicated through [Picot] Tremblay. Worries that JH has insufficient time and lags behind in the physical sciences. Comments on ideas put forward in 1824 by JH and discussed by MS. Has found MS's name connected with suspension bridge over Rhone River.

Thanks for and comments on paper and lectures on 'diathermancy &c' of gases, scientific teaching, and solar chemistry. Regrets that JT mentioned all names connected with light research except JH's. Remarks on absorption of light, molecular vibrations.

Does not believe surface of moon can radiate cold; perhaps new moon can. Explains this geometrically.

Outlines advantages of erecting great reflector in Melbourne [WW's colony] for observation of southern nebulae.

Encourages GA to develop some experiments to study the electrical phenomenon [see GA's 1861-9-23] more carefully.

Recognizes the validity of GA's claim to the eyepiece theory [see GA's 1861-3-27]; JH did not have space to deal adequately with the subject of telescopes.