A. Caverns, grottoes, and ruined abbeys; the areas of antique halls; the windings of long passages; the aisles of cathedral churches; mountains, and ice-bergs.
Q. Why are caverns, grottoes, and ruined abbeys famous for echoes?
A. 1st—Because the sound-waves cannot pass beyond the cavern or grotto, and must flow back:
2ndly—The return waves (being entangled by the cavern) are detained for a short time, and come deliberately to the ear.
Q. Why are antique halls, winding passages, and cathedral aisles famous for echoes?
A. Because the sound-waves cannot flow freely forward, but strike against the winding walls perpetually, and are beaten back.
Q. Why are mountains and ice-bergs famous for echoes?
A. Because they present a barrier to the sound-waves which they cannot pass; and are sufficiently elastic to throw them back.
Q. Why do not the walls of a room or church produce echo?