Note 522 — Chapter XV · [512]
Reading edition
The exact interval of the sparks was 0.00205''. The doubleness of their snap was usually replaced by a single-seeming sound when it fell to 0.00198'', the sound becoming louder when the sparks seemed simultaneous. The difference between these two intervals is only 7/100000 of a second; and, as Exner remarks, our ear and brain must be wonderfully efficient organs to get distinct feelings from so slight an objective difference as this. See Pflüger's Archiv, Bd. xi.