“Now, Tom,” said his father, “it is for you to explain the nature of the exhibition you have just witnessed.”
Tom proceeded accordingly.
“The bladder was highly elastic, and therefore readily yielded to the pressure of the air, and became distended. As soon, however, as the pressure was removed, the air was driven out again with force, and the particles of the Indian rubber returned to their former condition. But I observed one circumstance which I do not understand,” said Tom: “when you first turned the stop-cock, the air rushed out with great violence, and the ball diminished very rapidly; but it gradually slackened, until, at last, the bladder could scarcely be seen to contract.”
“I rejoice to find that you were so observant,” said his father: “the effect you noticed depended upon a general law of elasticity. Elastic bodies, in the recovery of their forms from a state of compression, after the removal of the compressing force, exert a greater power at first than at last, so that the whole progress of restoration is a retarded motion.”
The vicar, who had listened with profound attention to the explanation which the boy had offered, rushed forward at its conclusion, and clasping him in his arms, declared, that a first-class man of Trinity could not have succeeded better.
“But let us now, if you please, Mr. Seymour, suspend our researches: recollect,” said the vicar, “that your birds are, as yet, scarcely fledged; and they will, therefore, make greater advances by short flights frequently repeated, than by uninterrupted progression.”
We heartily concur in this opinion, and shall, therefore, terminate the chapter.
[11]. Upon this subject, Dr. Brewster’s Introductory Letter on Natural Magic will be read with interest and advantage.
[12]. The comparative inelasticity of water will be shown hereafter.