The pieces of furniture usually associated with him are massive structures of ebony with their surfaces covered with tortoiseshell, in which are inlaid arabesques, scrolls, and foliage in thin brass or other metal. Upon the surface of this metal inlay further ornamentation was chased with the burin. This alternation of tortoiseshell and brass forms a brilliant marquetry. Into the chased designs on the metal a black enamel was introduced to heighten the effect, which was further increased by portions of the wood beneath the semi-transparent tortoiseshell being coloured black or brown or red; sometimes a bluish-green was used. Later imitators, not content with the beautiful effect of tortoiseshell, used horn in parts, which is more transparent, and they did not fear the garish effect of blue or vermilion underneath. Boule's creations, set in massive mounts and adornments of masks and bas-reliefs, cast in gilt-bronze and chased, were pieces of furniture of unsurpassed magnificence, and especially designed for the mirrored splendours of the _salons_ of Versailles. In boule-work all parts of the marquetry are held down by glue to the bed, usually of oak, the metal being occasionally fastened down by small brass pins, which are hammered flat and chased over so as to be imperceptible. In order to economise the material, Boule, when his marquetry became in demand, employed a process which led to the use of the technical terms, _boule_ and _counter-boule_. The brass and the tortoiseshell were cut into thin sheets. A number of sheets of brass were clamped together with the same number of sheets of tortoiseshell. The design was then cut out, the result being that each sheet of tortoiseshell had a design cut out of it, into which the same design from one of the sheets of brass would exactly fit. Similarly each sheet of brass had a design cut out of it into which a corresponding piece of tortoiseshell would fit. That in which the ground is of tortoiseshell and the inlaid portion is brass, is considered the better, and is called _boule_, or the _premiere partie_. That in which the groundwork is brass and the design inlaid is of tortoiseshell, is called _counter-boule_ or _contre-partie_. This latter is used for side panels. An examination of the specimens preserved in the Louvre, at the Jones Bequest at the Victoria and Albert Museum, or in the Wallace Collection will enable the student to see more readily how this practice works out in the finished result. In the illustration (p. 163) of the two pedestals the effect of the employment of _boule_ and _counter-boule_ is shown. [Illustration: (_a._) (_b._) PEDESTALS SHOWING BOULE AND COUNTER-BOULE WORK. (_Wallace Collection._) (_a_) Boule or _premiere partie_. (_b_) Counter-boule or _contre-partie_.]