4 April 1834

This is a dictated letter, but the valediction at the end is in Herschel’s hand.

Dominique Francois Jean Arago (26 February 1786 – 2 October 1853), was a French mathematician, physicist, astronomer, freemason, supporter of the Carbonari revolutionaries and politician.

As a reward for his adventurous conduct in the cause of science, he was elected a member of the French Academy of Sciences, at the remarkably early age of twenty-three, and before the close of 1809 he was chosen by the council of the École Polytechnique to succeed Gaspard Monge in the chair of analytical geometry. At the same time he was named by the emperor one of the astronomers of the Paris Observatory, which was accordingly his residence till his death. It was in this capacity that he delivered his remarkably successful series of popular lectures in astronomy, which were continued from 1812 to 1845

Sir John Frederick William Herschel 1st Baronet KH FRS (7 March 1792 – 11 May 1871).

Herschel was an English polymath active as a mathematician, astronomer, chemist, inventor and experimental photographer who invented the blueprint and did botanical work.

Herschel originated the use of the Julian day system in astronomy. He named seven moons of Saturn and four moons of Uranus – the seventh planet, discovered by his father Sir William Herschel. He made many contributions to the science of photography, and investigated colour blindness and the chemical power of ultraviolet rays. His Preliminary Discourse (1831), which advocated an inductive approach to scientific experiment and theory-building, was an important contribution to the philosophy of science.

R5,000