A. 1st—Glass is sonorous; and the air communicates its vibrations to the glass, which echoes the same sound: and
2ndly—The window-frame is shaken by the sound-waves impinging against the window, and contributes to the noise.
CHAPTER XXIX.
MISCELLANEOUS.
Q. Why do the bubbles in a cup of tea range round the sides of the cup?
A. Because the cup attracts them.
Q. Why do all the little bubbles tend towards the large ones?
A. Because the large bubbles (being the superior masses) attract them.
Q. Why do the bubbles of a cup of tea follow a tea-spoon?