Various remarkable echoes, and some not very credible, have been described by different authors. Dr. Plott mentions an echo in Woodstock Park, which repeats seventeen syllables by day and twenty by night. The famous echo at the Marquess Simonetta's villa, near Milan, has been described both by Addison and Keysler. According to the last of these travellers, it is occasioned by the reflection of the voice between the opposite parallel wings of the building, which are fifty-eight paces from each other, without any windows or doors, and perpendicularly to the main body of the building. The repetition of the sound dwells chiefly on the last syllable. A man's voice is repeated about forty times, and the report of a pistol about sixty times; but the repetitions are so rapid, that it is difficult to number them, unless it be early in the morning, or in a calm, still evening. A curious example of an oblique echo, not heard by the person who emits the sound, is described in the "Memoirs of the Academy of Sciences" as existing at Genefay, near Rouen. A person singing hears only his own direct voice, while those who listen hear only the echo, which sometimes seems to approach, and at other times to recede from, the ear; one person hears a single voice, another several voices; one hears the echo on the right, and another on the left--the effect constantly changing with the position of the observer. One of the most remarkable echoes of which we have read is that which Dr. Birch describes as existing at Roseneath, in Argyllshire. When a person at a proper distance played eight or ten notes on a trumpet, they were correctly repeated, but a third lower; after a short silence, another repetition was heard in a yet lower tone, and alter another short interval, they were repeated a third time in a tone lower still. We extract the following account of two very interesting echoes from Mr. Herschell's work:-- "In the cathedral of Girgenti, in Sicily, the slightest whisper is borne with perfect distinctness from the great western door to the cornice behind the high altar, a distance of 250 feet. By a most unlucky coincidence, the precise focus of divergence at the former station was chosen for the place of the confessional. Secrets never intended for the public ear thus became known, to the dismay of the confessors and the scandal of the people, by the resort of the curious to the opposite point (which seems to have been discovered accidentally), till at length one listener, having had his curiosity somewhat overgratified by hearing his wife's avowal of her own infidelity, this tell-tale peculiarity became generally known, and the confessional was removed.[2]