Comments on analytic symbolism in mathematics.

Is trying to assist in finding someone to review a book [The Heavens] by [Amédée] Guillemin.

Describes experiment involving viewing spectrum of a light flash as it advances and recedes. [Marked 'not sent on further consideration.']

Comments further on Ernst Klinkerfüss's work [see JH's 1866-2-28]; on the behavior of light emitted by an electric spark.

Thinks William Whewell's excitement may be a 'precursor to exhaustion.' The hope of recovery is very slight. JH is interested in Whewell's article on Plato.

Thanks WS for communicating the events of William Whewell's last days.

Agrees to WJ's request to make use of an earlier letter of JH's [see WJ's 1866-3-7].

Will subscribe to HS's work as requested [see HS's 1860-3-5], but dissents 'from very large portions' of HS's views. Especially objects to HS's adoption of the 'Shibboleth of the Hegel & Schelling School of German Philosophy—"the Absolute."' [This letter misdated; correct date: 1860-3-17.]

FW's suggestion to collect William Herschel's published works into one volume was considered earlier, but publishers found it not profitable. All works except two are in R.S.P.T., 1780-1818. [Letter continues 22 Mar.:] JH almost completed identifying and assembling all of WH's double stars and micrometrical measures. Thanks for calling attention to 'unpublished series of 400 'Guages [sic] ('hausters')" noticed by [Maximilian Weisse]. JH was not aware of these. [Letter continues 23 Mar.:] Does not approve of FW's suggestion to request subscriptions to fund collection of WH's works. [Note by copyist: List of differences between original letter and copy.] [Unknown annotation: 'Original in No. 2 Corresp. Tin box B.8.']

Corrections to reports in 12 Mar. 1866 issue of Les Mondes regarding ecclesiastical titles in England, William Whewell's career, and W. T. Brande's role at Royal Mint. Also, English do not eat cats; 'catsup' is made of vegetables. Nor was JH's daughter [Maria Sophia] ever acquainted with late [Ludovico] Calandrelli.

Discusses how to denote the positions of the celestial bodies in solar photographs. Advocates a system that shows differences of heliocentric longitude on the sides of the sun.

As executor for estate of late [Thomas] Baldwin, JH received OH's certificate and order for payment to Mrs. Baldwin. Concern for Mrs. Baldwin's advanced age and her lax method of writing checks. Disposition of estate after Mrs. Baldwin dies.

Helioautographs are beautiful. Advises keeping original plan for presentation. Says 'Clarke's' [Harvey Carlisle's] article on William Whewell in MacMillan's is satisfactory. Describes an 'absurd paragraph' regarding Whewell in François Moigno's Mondes.

Comments on JH's health, the death of William Whewell, and extended comments on a mathematical proof provided by AD [see AD's 1866-4-1].

Mostly talks about having been offered some money to pay for the reduction of William Herschel's [JH's father] double star observations in preparation for publication.

Comments on the quality of the star catalogue of Charles Rümker [see John Wrottesley's 1866-4-16].

Comments on William Whewell's replacement on the Royal Observatory's Board of Visitors.

Inquires of GA as to the current status of parliamentary moves to introduce the metric system into Britain [see GA's 1864-9-28].

Thanks CP and R.A.S. Council for funds to help with JH's catalogue of William Herschel's double stars. Alexander Herschel will begin work soon on the project.

In response to FK's 1866-4-17, JH says that he knows nothing about screw propulsion in ships and so cannot comment on FK's paper.