The son of this man (who lived at Geneva), was no less skilful a mechanician, for he made a gold snuffbox about 4-1/2 inches long by 3 inches broad, in which when a spring was touched a little door flew open and a beautifully modelled bird of green enamelled gold rose up, fluttered its wings and tail, and commenced a trilling song of great beauty and power, its beak keeping time with the notes. Such a snuffbox was exhibited in the Great Exhibition of 1851, proving as great a popular attraction as the Koh-i-nur diamond, and (owing to the kindness of my friend Mr. Tripplin the well-known horologist) I am now able to show you one of these very beautiful triumphs of mechanical skill. Another of the younger Le Droz’s inventions was his celebrated drawing automaton, which was a life-size figure of a man sitting behind a table and holding a style in his hand. A sheet of vellum was placed on the table, and the figure began to draw portraits of well-known persons with extraordinary correctness. This automaton was shown in London, and attracted considerable attention at the time. [Illustration: Fig. 22.] I must now re-introduce to you another old friend, first shown here by Brother Manning. Here he is! a little acrobat that turns somersaults backwards down stairs. This is not, as many have thought, an invention of that great mechanical genius, Robert-Houdin, for it is figured and described in Musschenbroeck’s “Introductio ad philosophiam naturalem,” which was published in Leyden in 1762 (a year after the author’s death), and half a century before Robert-Houdin was born, and on the screen you have a facsimile (Fig. 22) of Musschenbroeck’s illustration of this mechanical toy, which he refers to as “an old invention of the Chinese.” It is also described by Ozanam in his “Recréations Mathématiques et Physiques,” the first edition of which was published in 1694. The figure I now throw on the screen (Fig. 23), is taken from the second edition of this work which was edited by Montucla in 1790. The principle is exceedingly simple; the whole thing depends upon the centre of gravity being suddenly changed by a shifting weight. Within a tube contained within the body, is a small quantity of mercury, and the moment that this tube is inclined to the horizon the mercury flows to the lower end tilting one figure over the other, and with such force that it is carried over by its inertia far enough to tilt the tubes, and cause the mercury to flow to the opposite end, and the process is repeated as long as there are stairs to descend; by a very simple arrangement of strings passing over pulleys, the legs and arms are always brought into suitable positions to support the figure in every position of its descent. [Illustration: Fig. 23.]