suspicious. The only gods they truly worshiped were honor

The intensity of a sound already heard may be of considerable influence. Certain experimenters have indicated the remarkable character of slightly intensive effects of sound. If you hold a watch so far from the ear as to hear it clearly but weakly, the sound decreases until finally it is not heard at all, and after awhile it is again heard, etc. This may lead to hearing distinct sounds made up of many tones, and need not evince any great illusion with regard to the ticking of a watch. But the thing may occur also in connection with more powerful and more distant sounds, e. g., the murmur of a brook, the rush of a train, the pounding in a distant factory. Noises far removed are influenced by reflections of sound, waves of air, etc., and it is possible that all kinds of things may be heard in a completely monotonous noise. This can be easily learned by listening to the soft murmur of a distant brook at night. Given the disposition and supposing the existence of the brook unknown, it is easy to hear in its monotonous murmur, human voices, sighs, shrieks, etc.

Another remarkable observation shows that in the dark very distinct things are heard during the playing of delicate instruments, such as mouth-organs. The humming approaches and withdraws, then it comes on various sides, and finally one has the feeling that the whole room is full of humming and winging insects. And this may go on indefinitely. There is a large collection of reasons for this reduplication of monotonous sounds. Everybody knows the accord of the olian harp which consists of identical notes, and the melodies which seem to lie in the pounding of the train on the rails. This can become especially clear when one is half asleep. If ever thinking begins to be ousted by slumber, the rhythmic pound begins to dominate consciousness. Then the rhythm gets its appropriate melody which becomes progressively more intense, and if one grows suddenly wide awake one wonders why the clearly-heard music is missing. Similarly, it is often asserted that a row of travelling wild swans make pleasant chords, although each swan is able to utter

only one cry. Difference in distance and alterations in the air cause the chords.

The difficulties in distinguishing the intensity or weakness of a sound are of importance. Fechner learned from the violinist Wasilewski that he observed that a male choir of four hundred voices did not sound essentially louder than one of two hundred. At the same time one clock is not heard at a great distance, a hundred clocks are heard. One locust can not be heard eating; when 1000 eat they are heard; hence each one must make a definite noise.[1] Early authorities have already indicated how difficult it is to distinguish the number of bells ringing together. Even musicians will often take two or three to be five or six.

Certain dispositions make some difference in this respect. The operating physician hears the low groaning of the patient after the operation without having heard his loud cries during the operation. During the operation the physician must not hear anything that is likely to disturb his work, but the low groan has simply borne in upon him. The sleeping mother often is deaf to considerable noise, but wakes up immediately when her child draws a deeper breath than usual. Millers and factory hands, travellers, etc., do not hear the pounding of their various habitual environmental noises, but they perceive the slightest call, and everybody observes the considerable murmur of the world, the sum of all distant noises, only in the silence of the night that misses it.

Illusions of direction of sound are very common. It is said that even animals are subject to them; and everybody knows how few human beings can distinguish the source and direction of street music, a rolling wagon, or a ringing bell. Even when long practice enables one to determine direction with correctness, an accidental event, perhaps the weather, especial sounds, a different grouping of individuals on the street, may result in serious mistakes. I tried to learn to judge from my office-desk whether the ring of the horse- car came from above or below. I succeeded so well that I could not understand how it was difficult not to learn the difference, and yet I failed many a time altogether in judgment. The reason for it I do not know.

All these enumerated circumstances must show how very uncertain all acoustic perceptions are, and how little they may be trusted if they are not carefully tested under similar conditions, and if--what is most important--they are not isolated. We are here led back

[1] Max Meyer: Zur Theorie der Geruschempfindungen. Leipzig 1902.

to the old principle that every observation is not proof but means of proof, and that it may be trusted only when it is confirmed by many parallel actions which are really consistent. That even after that mistakes are possible, is true, but ``after that'' is when we have done all that lies within human power.