“Well, then, I will put your knowledge to the test,” observed Mr. Seymour, “for you shall explain to me the mechanism of these _Chinese Tumblers_.” Upon which he produced an oblong box, which, by opening, formed a series of stairs or steps, and took from a drawer at its end two grotesque figures (_Clown_ and _Pantaloon_), which were connected with each other by two poles, which they appeared in the attitude of carrying, pretty much in the way that the porters carry the poles of a sedan-chair. The foremost figure was then placed upon the top step, when, to the great astonishment of the whole party, the figures very deliberately descended the several stairs, each turning over the other in succession. “There was a period in our history,” observed Mrs. Seymour, “when so marvellous an exhibition would have subjected the inventor to the penalties of sorcery.” “That,” remarked Mr. Seymour, “may be said of most of the other inventions which I have yet in store to illustrate the powers conferred upon us by a knowledge of natural philosophy; but, as far as mechanical skill is concerned, I doubt whether the ancients did not even surpass us, especially in the art of constructing automata; and as quicksilver was known in the remotest ages, I think it not improbable that it was one of the agents employed by them on such occasions. If I remember right, Aristotle describes a wooden Venus, which moved by means of ‘_liquid silver_;’ then, again, the moving tripods which Apollonius saw in the Indian temples--the walking statues at Antium, and in the temple of Hierapolis, and the wooden pigeon of Archytas,[11] ought, undoubtedly, to be regarded as evidences of their mechanical resources. But let us reserve these literary questions for the better judgment of our worthy friend the vicar, and proceed to consider the mechanism of the toy before us. Tom,” continued he, “take the figures in your hand and examine them.” No sooner had the young philosopher received the figures from the hand of his father than he declared that the tubes were hollow, and that he felt some liquid running backwards and forwards in them. “You are quite right, my boy,” said Mr. Seymour, “they contain quicksilver.” “Now then I understand it,” cried Tom; “the quicksilver runs down the tubes and alters the centre of gravity of the figures, and so makes them tumble over each other.” “Well, I acknowledge that is no bad guess as a beginning, and will certainly explain the first movement; but you will be pleased to recollect that the instant a new centre of gravity is thus produced the figures must remain at rest--how, then, will you explain their continued motion?” “You said something, I think, about momentum; did you not, papa?” “Certainly; and to its agency the continuance of the motions is to be ascribed: but I will explain the operation more fully.”