The object of crayon engraving is to imitate the effect of red or black chalk on a coarse-grained paper, which, by the very roughness of its surface, retains no more than an uneven, and as it were a disconnected, impression of the strokes or hatchings laid upon it. In common with stipple engraving, it renders the loose and broken lines of the originals by substituting a mass of dots for the ordinary work of the burin or the needle. It differs, however, from stipple engraving in the method of working, and even in the nature of the tools employed. The outlines are traced on the varnished copper with a toothed or multi-pointed needle, while the inner hatchings are made either with the needle in question, or with what is called a roulette, which is a steel cylinder bristling with small, jagged teeth, and running on a fixed axis. The roulette, which is provided with a handle, is so directed that the teeth are brought to bear directly, and with more or less effect, on the varnished copper. Then the plate is bitten in; and when the aquafortis has done its part, the work, if necessary, is resumed with the same tools on the bare metal. The first specimens of crayon engraving were presented in 1757 to the Académie Royale de Peinture, which, an official document informs us,[48] "highly approved of the method, as being well fitted to perpetuate the designs of good masters, and multiply copies of the best styles of drawings." For the reproduction of drawings, the new process was certainly better than etching, at least as practised to that end by the Count de Caylus and the Abbé de Saint-Non. The misfortune was, that in the eighteenth century as in the first years of the nineteenth, the crayon engravers appear to have thought far less of "perpetuating the designs of good masters" than of suiting their choice of originals to the prevailing fashion. As a matter of fact, however skilful they were in execution, the only cause served by Demarteau's innumerable fac-similes was that of the Bouchers and Fragonards, and of kindred experts in "the most distinguished school of drawing." Reproduced by engraving, the crayon studies of these persons became the ordinary means of instruction in academies and public schools; and from the first the popularity of these wretched models was such that, even after the revolution effected in art by David, on through the Empire, and as late as the Restoration, art students generally remained subject to the regimen adopted for their predecessors in the days of Louis XV. and XVI.