It is this final period of Madame du Deffand’s life that is reflected so minutely in the famous correspondence which the labours of Mrs. Toynbee have now presented to us for the first time in its entirety.  Her letters to Walpole form in effect a continuous journal covering the space of fifteen years (1766-1780).  They allow us, on the one hand, to trace through all its developments the progress of an extraordinary passion, and on the other to examine, as it were under the microscope of perhaps the bitterest perspicacity on record, the last phase of a doomed society.  For the circle which came together in her drawing-room during those years had the hand of death upon it.  The future lay elsewhere; it was simply the past that survived there—­in the rich trappings of fashion and wit and elaborate gaiety—­but still irrevocably the past.  The radiant creatures of Sceaux had fallen into the yellow leaf.  We see them in these letters, a collection of elderly persons trying hard to amuse themselves, and not succeeding very well.  Pont-de-Veyle, the youthful septuagenarian, did perhaps succeed; for he never noticed what a bore he was becoming with his perpetual cough, and continued to go the rounds with indefatigable animation, until one day his cough was heard no more.  Henault—­once notorious for his dinner-parties, and for having written an historical treatise—­which, it is true, was worthless, but he had written it—­Henault was beginning to dodder, and Voltaire, grinning in Ferney, had already dubbed him ‘notre delabre President.’  Various dowagers were engaged upon various vanities.  The Marquise de Boufflers was gambling herself to ruin; the Comtesse de Boufflers was wringing out the last drops of her reputation as the mistress of a Royal Prince; the Marechale de Mirepoix was involved in shady politics; the Marechale de Luxembourg was obliterating a highly dubious past by a scrupulous attention to ‘bon ton,’ of which, at last, she became the arbitress:  ‘Quel ton!  Quel effroyable ton!’ she is said to have exclaimed after a shuddering glance at the Bible; ’ah, Madame, quel dommage que le Saint Esprit eut aussi peu de gout!’ Then there was the floating company of foreign diplomats, some of whom were invariably to be found at Madame du Deffand’s:  Caraccioli, for instance, the Neapolitan Ambassador—­’je perds les trois quarts de ce qu’il dit,’ she wrote, ’mais comme il en dit beaucoup, on peut supporter cette perte’; and Bernstorff, the Danish envoy, who became the fashion, was lauded to the skies for his wit and fine manners, until, says the malicious lady, ’a travers tous ces eloges, je m’avisai de l’appeler Puffendorf,’ and Puffendorf the poor man remained for evermore.  Besides the diplomats, nearly every foreign traveller of distinction found his way to the renowned salon; Englishmen were particularly frequent visitors; and among the familiar figures of whom we catch more than one glimpse in the letters to Walpole are Burke, Fox, and Gibbon.  Sometimes influential parents in England