Tom inquired what kind of bodies was most elastic. He was informed that the air was the most elastic of all known substances, and had, for that reason, been distinguished by the name of an elastic fluid. Hard bodies were so in the next degree; while soft substances which easily retain impressions, such as clay, wax, &c. might be considered as possessing but little elasticity.
“I should have thought,” said Louisa, “that neither clay nor wax had possessed any elasticity.”
“My love, we know not any bodies that are absolutely, or perfectly, either hard, soft, or elastic; since all partake of these properties, more or less, in some intermediate degree. Liquids are certainly the least elastic of all bodies; and, until lately, water was regarded as being perfectly inelastic;[[12]] but recent experiments have shown it capable of compression, and of restoring itself to its original bulk, as soon as the pressure is removed; it must, therefore, possess some elasticity. Indeed,” said Mr. Seymour, “we might have anticipated such a result from the effects which present themselves in the well-known game of ‘Ricochet,’ or Duck and Drake.”
“Duck and Drake!” exclaimed Louisa; “for goodness’ sake, what can that game be?”
“I dare say your brother will not have any difficulty in explaining it to you.”
Tom informed her that it was a game in which any number of boys threw a stone, or a flat piece of tile, into the water; and that he whose stone rebounded the greatest number of times was the conqueror.
“It is a very ancient game,” said Mr. Seymour, “and had the vicar been present, we should have heard a learned disquisition upon it; as he, however, is unfortunately absent, I must tell you all I know upon the subject. It was called by the Greeks Epostrakismos,[[13]] and was anciently played with flat shells. Now it is evident that the water must possess some degree of elasticity, or the stone could not rebound[(13)]; but I shall have occasion to revert to the subject hereafter.”
“And are my marbles elastic?” asked Tom.
“Undoubtedly; but not to the same extent as your ball. There,” said Mr. Seymour, throwing his ball against the wall, “see how it rebounds.”
“The return of the ball,” observed Tom, “was, I suppose, owing to its elasticity; and I now understand why one filled with air rebounds so much better than one stuffed with bran or wool.”