Page:Popular Science Monthly Volume 33.djvu/97

Rh the mother can be found. The child can not determine its mother's location by the sound of her voice. This exaggerated instance may be owing to the reflection of the sound, not only from the walls, but from the strata of air differing in temperature and humidity.

How many of us going to the next street, running at right angles to the car-tracks, can tell, from hearing the bell of the approaching street-car before the car comes in sight, whether that car is going north or south? It does not seem that animals can determine the direction of sound much better than man. The sleeping dog, roused by his master's call, is all abroad as to his master's location, and determines it by sight or scent, or both, frequently running in several different directions before hitting the right one. The deer, on being startled by the unseen hunter's tread, is not always right in his selection of the route to get out of harm's way. A flock of geese, ducks, or other birds, on hearing a gun, is as likely to fly toward as from the sportsman, if he has kept entirely out of sight, and the flash of his piece has not been seen.

It is a question whether the blind are better able to determine the direction of sound by ear than are seeing people. It is possible that their senses of touch and smell are so highly developed that their instantaneous action with that of the ear give them a decided advantage over seeing people in this matter. I have known a blind man to be so sensible of the current of air put in motion by the speaking of a single word in a room, that he could select the speaker by his location, though others were present. So, too, I have known a blind man to locate and identify the various people in the room, he saying he did it by the different scent evolved from each, the seeing people there not being sensible of any scent from any one. And yet he, when standing in the middle of the room with his nose stopped, could not give the direction of one single speaking person.

Prof. Alexander Graham Bell reports, in a paper he read before the American Association for the Advancement of Science at Saratoga in 1879, a series of experiments in binaural audition, showing, among other things, that direction can not be appreciated by monaural observation; that when the source of sound is at the nadir of the observer, the perception of its direction is absolutely unreliable, and that not one of the many on whom he tried the experiment had the slightest idea of the true direction of a sound produced beneath him.

We are so much accustomed to the aid of our other senses, especially that of sight, that we incline to give more value to audition in determining direction than it deserves. That is one reason why we err so largely when so placed that the eye can