The party accordingly left the Lodge, and when they had arrived at the fountain, their father produced a small wooden figure, of which the annexed is a sketch. Within its base was fixed a hollow sphere, or ball of thin copper, which, when properly adjusted on a fountain, or _jet d’eau_, was sustained by the momentum produced by the velocity of the stream; so that the whole figure was balanced, and made to dance on the fountain, as the pith-ball had been made to play in the current of air. [Illustration: Man sitting at the top of a fountain’s stream of water.] The children were much gratified at witnessing so curious an exhibition. Mr. Twaddleton laughed heartily at the ludicrous effect it produced, and observed that, although he had never before seen the experiment, he had frequently heard of it; and he added, that he understood it to be a very common toy in Germany and Holland. “I have for some time,” said Mrs. Seymour, “been trying to construct a light figure of this kind, which shall dance on a current of air; and I believe I have at length succeeded. The head I have formed of the seed vessel of the _Antirrhinum_, which has a striking resemblance to a face, and possesses, moreover, the indispensable condition of lightness. The dress is made of silver paper, stretched over a cone of the same material. From its appearance I have named it the _Flying Witch_.” “I admire your ingenuity,” said Mr. Seymour, “and I have no reason to doubt the success of your enterprise.” “I found it convenient,” continued Mrs. Seymour, “to place a stage of card below the orifice of the tube, in order to steady the figure as she rises, and to receive her as she falls.” “Your principal care,” observed her husband, “must be to throw the centre of gravity of the figure as low as possible.” On the party returning to the library, Mr. Seymour expressed a wish that, before they suspended their morning’s recreations, they should take into consideration a peculiar property of matter, which they had not yet discussed. “And what may that be?” asked Louisa. “ELASTICITY,” replied her father; “and I wish to hear whether Tom can explain to us the meaning of the term.” Tom very well knew what was meant by Elasticity; but he was like many a merchant with a bill of exchange, who, although well acquainted with its value, has not sufficient small change to cash it. Tom wanted words to enable him to furnish a clear definition; his father, therefore, kindly relieved his embarrassment, by informing him that “it was a property inherent in certain bodies, by which they possessed a disposition to have their form altered by force or pressure, and to recover it on the removal of that pressure, throwing off the striking body with some degree of force: for example,” continued he, “the cane which I hold in my hand can be bent to a certain extent, and then, if I let it go, it will immediately return to its former condition with considerable force.”