Describes prismatic spectrum of flame of cyanogen and offers to repeat experiment with Michael Faraday for JH's benefit.

Asks JH to clarify what goods are his from a joint order with WT from a German optical firm.

Queries and comments about telescopes and microscopes; some thoughts about a diffraction grating.

Renders an accounting of expenses for optical goods received from Germany.

Thanks WT for optical equipment sent. Notes death of Augustin Fresnel. Has purchased a telescope from James South.

Writes in favour of a London University professorship for Thomas Key. Refers to some optical experiments of Michael Faraday, and extends solution of conic section problem first raised in WT's letter of 1826-2-27.

Responds to WT's 1827-10-29. Sending JH's Light, which uses some of WT's publications.