Scholar and encyclopedist Warden's observations on politics, literature, medicine (in 1806, he formally enrolled in the
Ecole de Medicine de Paris), chemistry, natural science, and education resulted in a wide correspondence with, among others,
Alexander von Humboldt,
Joel Roberts Poinsett,
Alexander Dallas Bache, the
Marquis de Lafayette,
Joseph Louis Gay-Lussac,
Washington Irving and
Thomas Jefferson. In 1809, Warden was elected as a member of the
American Philosophical Society in
Philadelphia. In France, as a friend of leading French writers and intellectuals, Warden offered assistance to visiting scholars from America providing a bridge between the European and American intellectual communities. In 1819 his publication, in three volumes, of
A Statistical, Political and Historical Account of the United States of America helped secure his election in 1826 as a corresponding member of the
Académie des sciences, Morales et Politiques. The publishers of the encyclopedic series, ''L'art de vérifier les dates'', commissioned him to research the volumes on North and South America in 1821. These ran to ten volumes and were written over thirteen years. In a "biographical sketch" of Warden's years in Paris published by the Institut Francais de Washington, Francis C. Haber described him as "America's cultural ambassador". Warden was "among the active core" of the
Société de géographie. With
Edmé-François Jomard (an engineer-geographer in
Napoleon's scientific expedition to Egypt in 1798), he was behind the society's patronage of studies of
Mesoamerica. Their terms for a competition for the best new work on "American antiquities", including maps "constructed according to exact methods" and "observations on the mores and customs of the indigenous peoples, and vocabularies of the ancient languages". extended decades-old scientific practices to a new field of anthropological inquiry. Warden himself never returned to Ireland, although others who left under the same circumstances as himself did so with relative impunity. When in the United States he had shared articles from Irish journals, including the
Belfast Monthly Magazine produced by the initiator of the United Irish movement,
William Drennan. after the diplomatic restraint of U. S. Service Warden no longer seemed engaged with Ireland politically. His papers reveal encounters with visiting Irish writers, among them
John Banim,
Maria Edgeworth and
Thomas Moore. The circle they suggest, however, does not include Irish political exiles in the French capital. Warden does not appear to have regularly associated in Paris with
Myles Byrne,
William Putnam McCabe or
John Allen, men who had assisted
Robert Emmet in his attempt to renew the United Irish insurrection with a
rising in Dublin in 1803. Byrne, however, does record in his memoirs an incident in 1820 when both he and Warden were together of assistance in Paris to the widow of
Reverend William Jackson, "one of the first martyrs to the independence of his native land" (Jackson had been executed as a French agent in Dublin following contact with Tone in 1794). On the title pages of his published works, Warden credited himself as a corresponding member of the
Belfast Literary Society. The society avoided political topics: Warden was elected in recognition of on an American journal he had kept on weather, disease, and meteorological phenomena. Warden did maintain a correspondence with
William Sampson, a United Irish exile in New York, who had been three years in Paris. But their common interest was broader than Ireland. Sampson was counsel for the abolitionist
Manumission Society and victor in the case
People v. Phillips (1813) which secured recognition in the United States for
priest-penitent privilege. Warden was able to communicate
Grégoire's high praise for Sampson's defence of religious toleration. After the
union with Great Britain, Ireland had seen the birth of a new, overwhelmingly Catholic, national movement under
Daniel O'Connell. Hailing him on his death in 1847 an "incarnation of a people",
Honoré de Balzac noted that for twenty years O'Connell's name had filled the press of Europe as no man since Napoleon. Of this in Warden's extensive, wide-ranging, correspondence there appears to be no record.
Published works • 180? (under the alias William Fox),
A Narrative of the Principal Proceedings of the Republican Army of the County of Down. National Archives of Ireland 620/4/41 • 1802:
A sermon on the advantages of education: preached in the Reformed Dutch Protestant Church, Kingston, on the 30th of April, 1802 • 1804:
The frame of the material world manifests, that there must be a god: a discourse on the ensuing words of the book of psalms: delivered before the students in Kingston Academy • 1808: (Translator) Antoine Léonard Thomas,
Eulogium on Marcus Aurelius • 1810: (Translator) Henri Grégoire,
An enquiry concerning the intellectual and moral faculties, and literature of Negroes. Brooklyn, Thomas Kirk. • 1813:
On the Origin, Nature, Progress and Influence of Consular Establishments. Paris, Smith, Rue Montmorency. • 1816:
Chorographical and Statistical Description of the District of Columbia. Paris, Smith, Rue Montmorency • 1819:
A Statistical, Political, and Historical Account of the United States of North America 3 vols., A. Constable and Co, Edinburgh; T. Wardle, Philadelphia. • 1820:
Bibliotheca America Septentirionalis. Paris, L'imprimerie de Nouzou • 1825:
Description Geographique et Historique du Bresil, Paris, Madame Huzard. • 1827: ''Recherches sur les antiquités de l'Amérique Septentrionale''. Paris, Everat, Imprimeur-Libraire. • 1829: ''Notice Biographique Sur Le Général Jackson, Président Des États-Unis de l'Amérique Septentrionale'', Barrois Aine-Libraire • 1831:
Bibliotheca Americana: Being a Choice Collection of Books Relating to North and South America and the West-Indies. Paris • 1832–1844:''L'art de vérifier les dates des faits historiques, des chartes, des chroniques et autres anciens monuments, depuis la naissance de Notre-Seigneur'', Vols. [33–37 and 39–44] written under the running title "Chronologie historique de l'Amerique." Paris, Moreau imprimeur. ==Death==