BONHEUR DU JOUR  , the name for a lady's writing-desk, so called because, when it was introduced in France about 176o, it speedily became intensely fashionable . The bonheur du jour is always very light and graceful; its special characteristic is a raised back, which may form a little cabinet or a nest of drawers, or may simply be fitted with .a mirror . The top, often surrounded with a chased and gilded bronze gallery, serves for placing small ornaments . Beneath the writing surface there is usually a single drawer . The details vary greatly, but the general characteristics are always traceable . The bonheur du jour has never been so delicate, so charming, so coquettish as in the quarter of a century which followed its introduction . The choicer examples of the time are inlaid with marqueterie, edged with exotic woods, set in gilded bronze, or enriched with panels of Oriental lacquer .