Consists of about 50 letters to Guillemard's nieces, Frances Griffin (d. 1868), Jane Griffin Franklin (1791–1875), and Mary Griffin (1793–1854), from London, Tredrea (the Cornish home of Guillemard's brother-in-law Davies Giddy), Clavering, Paris, Florence, Rome, Naples and elsewhere.

Childless himself, Guillemard treated his nieces as though they were his own children. He was very interested in their education, and his letters include discussion of ideas and developments in the intellectual milieu in which he moves; book recommendations; and reports on meetings with the savants of Europe, Constantin François de Chassebœuf, comte de Volney in particular.

His letters document his time on the Continent, primarily France and Italy, between 1814 and 1818. While in the former, he stays with his friend, François Alexandre Frédéric de la Rochefoucauld-Liancourt, renews his acquaintance with some of the country's aristocratic families, and visit scientists and a number of the English residents in Paris. Letters of his trip to Italy include descriptions of the Neapolitan War.