Soon after his mind began to give way, but during frequent intervals of lucidity he made new corrections in his great work, of which a third edition appeard in 1744, prefaced by a letter of dedication to Cardinal Trojano Acquaviva.
He died on the 18th of May 1807, and a volume of Miscellaneous Works, prefaced by a short biography, was published in 1820.
To his translation (1530) of a Latin Chronicle and Description of Turkey, by a Transylvanian captive, which had been prefaced by Luther, he added an appendix holding up the Turks as in many respects an example to Christians, and presenting in lieu of the restrictions of Lutheran, Zwinglian and Anabaptist sects, the vision of an invisible spiritual church, universal in its scope.
A new edition of the complete translation, prefaced by a letter on Gibbon's life and character, from the pen of Suard, and annotated by Guizot, appeared in 1812 (and again in 1828).
He edited in 1860 The Atonement, a collection of essays by various hands, prefaced by his study of the "Rise of the Edwardean Theory of the Atonement."