Page:Popular Science Monthly Volume 33.djvu/98

88 not correct the error of the ear—in fact, many people seem to be unaware that they have any inability to locate sound by the ear until they have learned the fact by experience, and even then they appear to consider marked instances as abnormal.

It is sufficiently easy to account for aberrations of audition as to the direction of sound from objective causes, such as reflection, diffraction, and deflection of sound-waves. But it may also often be accounted for by what Prof. Henry called subjective causes, such as induce belief that an anticipated sound has come from a specified direction, when it has really come from quite another direction. Here the personal equation of the listener must be largely taken into consideration. The success of the ventriloquist may also depend upon subjective causes.

President Welling tells us something of how Prof. Henry, when at Princeton, induced subjective causes in his pupils, to their bewilderment, making them believe, for the moment, that a given sound came from a specified corner of the class-room, when it really came from quite a different direction.

Mariners are beginning to accept the fact that they may err in assigning the true direction to sound; but their ideas on the subject are still vague and indeterminate. Hence occur collisions between ships at sea, and lawsuits between their owners on shore. The collision at 10, on September 21, 1882, between the Dutch steamer Edam and the British steamer Lepanto, on George's Bank, Atlantic Ocean, when the former was sunk by the latter, resulted in a suit in the United States District Court at New York city, in which the case turned on an erroneous location of the Edam by the Lepanto, on hearing the sound of her fog-horn. The court dismissed the case with costs, holding that "an error of five points in locating a vessel's position by the sound of her whistle in a fog is not necessarily a fault under the proved aberrations in the course of sound." The judge, in his decision, quotes, among others, papers read before the Washington Philosophical Society as his authority for certain statements he makes as to these laws of sound bearing on the case.

As it seems evident that the unassisted ear is likely to err in determining the location of sound, the question arises, Can the ear be aided in this matter? Apparently this is possible. Prof. Mayer, of the Institute of Technology at Hoboken, N. J., has, to a certain extent, solved this problem by the construction of an instrument called the "topophone," by the use of which President Morton, a member of the Lighthouse Board, was enabled to locate within ten degrees, or less than one compass-point, the sound of a fog-signal, when in the cabin of a steamer