He worked chiefly for Jombert, a sort of learned bookseller, King's printer for the artillery, who dates from July, 1736. Jombert was visited by painters. He gave little private soirées, which Cochin attended, and where he daily made numerous friends. It was in this house, of so special a character, and, it may be said, so little artistic at first sight, that Cochin invented his best frontispieces, among them that of the _Calcul Différentiel_, that of the _Astronomie Physique_, and the plates of the _Méthode de Dessin_, after Boucher. He was one of the first to produce engraved titles, with which the publisher Prault ornamented his dainty volumes, and which were imitated, up to the end of the eighteenth century, by all the illustrators who followed. In that to the works of Madame Deshoulières the letter itself is engraved. Since then the open letter has been copied in typography. These vignettes were used many times by publishers, sometimes simply effacing the inscription, sometimes reproducing the original design by a different artist. The boy with the swan had decorated in 1744 a "Jerusalem Delivered" in Italian, by the same publisher, Prault; it was then engraved by Aveline. Fessard engraved the second plate, which is here reproduced. [Illustration: Fig. 82.--Title-page engraved by Fessard after Cochin for the works of Madame Deshoulières, 1747.] Nearly all the frontispieces of the Book with vignettes of the eighteenth century preserve this arrangement: an ornamented and draped border, with garlands of roses, symbols, and cupids, in the middle the title, in red and black, composed in open letter, often a scroll with the address of the publisher, but rarely a mark. It was the time of little winged cupids, goddesses, and gods. The goddesses were the favourites of the kings, Madame de Pompadour or the princesses, but rarely the virtuous Marie Leczinska, too homely and too much ignored to tempt the artists; the kings or the princes were the gods. After Jombert, Prault, and Coustellier, Cochin worked for François Didot, syndic of the printers, for whom he prepared a set of illustrations to Molière. Unfortunately Didot died in 1757, and the project fell with him. Of the work of Cochin there only remains the set of _Tartufe_ etchings in octavo.