Echo
Echo names 3 different subjects across the 6 encyclopedias on this shelf. Each is set out below.
Echo ek'o, in Greek mythology
Aiton's Encyclopedia (1910)
ek'o, in Greek mythology, a beautiful nymph of the woodland hills. She was an attendant upon Artemis, the huntress. Her chief failing was a habit of talking too much and of insisting on having the last word. One day Hera was seeking her wayward husband, Zeus, whom she had reason to believe was disporting himself among the nymphs. Echo managed to detain Hera in conversation until Zeus made his escape. In her anger Hera deprived Echo of all power of speech save reply, that is, she left her only the last word. Echo fell in love with a beautiful youth named Narcissus. She followed him in the chase, waiting for him to speak that she might reply. At length the opportunity came, but Narcissus did not return her love. In her grief she faded and pined away until nothing was left but her voice, which may still be heard wandering in the mountains, speaking only when spoken to, and replying only in the exact words of the speaker.
Echo a sound returned to its source
Aiton's Encyclopedia (1910)
a sound returned to its source. If a person speaks against a wall or cliff the wave of sound is sent back again, and the speaker hears the sound of his own voice as though someone in the distance were calling to him. Under ordinary conditions sound travels at a rate of 1,080 feet per second. The time elapsing between the call and the return of an echo gives a clue to the distance of the reflecting surface. The reflecting surface must be a concave or, if flat, it must stand squarely across the path of the sound, or else the sound wave will glance off in another direction and fail to return to the speaker. Many caves and mountain passes have celebrated echoes. Some public halls echo to such an extent that it is difficult to address an audience. In such cases cloth hangings are a help.
Echo A daughter of the Air and Tellus
1000 Classical Characters (1900)
A daughter of the Air and Tellus, who was one of Juno 's attendants. She was deprived of speech by Juno, but was allowed to reply to questions put to her.
What Has Changed in the Last Century
Aiton's 1910 account of the nymph still stands as Ovid told it, and nothing has shifted there but the spelling of the gods' names. The physics section has aged more: the "1,080 feet per second" quoted is roughly the speed of sound at freezing point, while at ordinary room temperature it is nearer 1,125 feet per second, and the advice to hang cloth in echoing halls had already been turned into a science by Wallace Sabine, whose reverberation formula underpins the design of concert halls to this day. Deliberate echoes have since become instruments rather than nuisances: echo sounding was fitted to ships in the 1920s to measure ocean depth, and in 1938 Donald Griffin and Robert Galambos showed that bats navigate by their own returning cries, a trick Griffin later named echolocation. Medical ultrasound and radar work on the same principle the 1910 entry describes at a cliff face.
Written for this edition, 2026.