Discusses L. J. M. Daguerre's patent application, JH's experiments in making light sensitive paper, and JH's determination to give up photographic researches so as to return to preparation of JH's Cape Results.

Waited until after 14 Feb. to submit JH's paper on photography ['On the Chemical Action of the Rays of the Solar Spectrum...,' R.S.P.T. (1840), 1-59]. Will send WT a copy.

Sending specimens sent to JH by [Robert] Hunt. Praises Hunt. Has WT received JH's paper ['On the Chemical Action of the Rays of the Solar Spectrum...,' R.S.P.T. (1840), 1-59]? JH moving to Collingwood.

Thanks for excellent pictures WT sent. JH wishes JH had time for further experiments, especially on the 'thermic spectrum.' Praises [Robert] Hunt's results. Recommends experiment to WT.

Praises various photographs by WT and notes changes in some. Recounts optical experiments, recent and planned, by JH on rock-salt.

Sends WT a copy of the solar spectrum in which each color is represented clearly in a 'positive' picture. JH sees this as giving hope for color photography.

Praises WT for invention of 'Kalotype' process; predicts it will be called 'Talbotype.' Notes excellence for photography of the weather during past year. Mentions possibility of cases of excessively rapid photographic change.

Congratulates WT on the calotype invention and the patent. Responds at some length to WT's concerns about the infinity of the universe. In postscript, provides a 4-page dialogue on the subject.

A further two dialogues elaborating on JH's earlier arguments [see JH's 1841-3-18] on the infinity/finitude of the universe.

Doubts that isomerism of all elements can be verified experimentally, but notes a number of groups with similar atomic weights that might well fit. Further on vegetable colors in photography. Refers to enclosure of a further dialogue on infinity.

Has been experimenting with paper prepared with light-sensitive vegetable juices. Sends two specimens of JH's results.

Explains the operation of the Council of the R.S.L. and hopes that WT will treat their unintended slight as a 'gaucherie'.

Thanks for calotypes involving persons engaged in actions. Gives encouragement to WT's planned photographic tour in Germany. JH has been experimenting regarding color photography.

Comments on confusion between observing comet and zodiacal light. Extensive comments on various materials used in a photographic process where negatives change to positives over long time.

Zodiacal light is a real phenomenon. Further comments on negative to positive process. Questions whether WT can define one cometary orbit with two observations.

Thanks for excellent Talbotypes. Notes how few photographs are 'perspective representations on a vertical plane' and suggests how to correct this.

Refers WT to reference work to check WT's experiments [see WT's 1848-2-4]. JH says he will perform no more experiments in physical optics.

Appreciates WT's letter of congratulation on JH's appointment [as Master of the Mint, to the Cambridge Commission?]. Has begun work with Cambridge.

Agrees to WT's use of name 'amphitype' [see WT's 1851-5-6 or earlier].

Wants recommendation from WT for teacher of the 'art of Talbotyping.'