759, he
contributed an _Histoire de Posthume empereur des Gaules_ (vol. xxx.,
1760) to the collected works of that illustrious society, and also a
_Memoire sur l'etablissement de la religion et de l'empire de Mahomet_
(vol. xxxii., 1761-1763). After the close of the Seven Years' War he was
sent to search in the archives of England for documents bearing upon the
history of France, more particularly upon that of the French provinces
which once belonged to England. This mission (1764-1766) was very
fruitful in results; Brequigny brought back from it copies of about 7000
documents, which are now in the Bibliotheque Nationale. A useful
selection of these documents was published (unfortunately without
adequate critical treatment) by Jean Jacques Champollion-Figeac, under
the title _Lettres de rois, reines et autres personnages des cours de
France et d'Angleterre, depuis Louis VII. jusqu'a Henri IV., tirees des
archives de Londres par Brequigny_ (collection of _Documents inedits
relatifs a l'histoire de France_, 2 vols., 1839, 1847). Brequigny
himself drew the material for many important studies from the rich mine
which he had thus exploited. These were included in the collection of
the Academie des Inscriptions: _Memoire sur les differends entre la
France et l'Angleterre sous le regne de Charles le Bel_ (vol. xli.);
_Memoire sur la vie de Marie, reine de France, soeur de Henri VIII., roi
d'Angleterre_ (vol. xlii.); four _Memoires pour senir a l'histoire de
Calais_ (vols. xliii. and l.); and _Memoire sur les negotiations
touchant les projets de mariage d'Elizabeth, reine d'Angleterre, d'abord
avec le duc d'Anjou, ensuite avec le due d'Alencon, tons deux freres de
Charles IX._ (vol. l.). This last was read to the Academy on the 22nd of
January 1793, the morrow of Louis XVI.'s execution. Meanwhile, Brequigny
had taken part in three great and erudite works. For the _Recueil des
ordonnances des rois de France_ he had prepared volumes x.-xiv., the
preface to vol. xi. containing important researches into the French
communes. To the _Table chronologique des diplomes, chartes, lettres, et
actes imprimes concernant l'histoire de France_ he contributed three
volumes in collaboration with Mouchet (1769-1783). Charged with the
supervision of a large collection of documents bearing on French
history, analogous to Rymer's _Foedera_, he published the first volume
(_Diplomatat. Chartae_, &c., 1791). The Revolution interrupted him in
his collec