To the quantitative analysis of the intensive relations presented by beaten rhythms must be added the evidence afforded by the apprehension of auditory types.  When a series of sounds temporally and qualitatively uniform was given by making and breaking an electric circuit in connection with a telephone receiver, the members of a group of six observers without exception rhythmized the stimuli in groups—­of two, three and four elements according to rate of succession—­having initial accentuation, however frequently the series was repeated.  When the series of intervals was temporally differentiated so that every alternate interval, in one case, and every third in another, stood to the remaining interval or intervals in the ratio, 2:1, the members of this same group as uniformly rhythmized the material in measures having final accentuation.  In triple groups the amphibrachic form (in regard to temporal relations only, as no accentuation was introduced) was never heard under natural conditions.  When the beginning of the series was made to coincide with the initiation of an amphibrachic group, four of those taking part in the investigation succeeded in maintaining this form of apprehension for a time, all but one losing it in the dactylic after a few repetitions; while the remaining two members were unable to hold the amphibrachic form in consciousness at all.

(b) The Distribution of Durations.

The inquiry concerning this topic took the direction, first, of a series of experiments on the influence which the introduction of a louder sound into a series otherwise intensively uniform exerts on the apparent form of the series within which it occurs.  Such a group of experiments forms the natural preliminary to an investigation of the relation of accentuation to the form of the rhythm group.  The apparatus employed was the fourth in the series already described.  The sounds which composed the series were six in number; of these, five were produced by the fall of the hammer through a distance of 2/8 inch; the sixth, louder sound, by a fall through 7/8 inch.  In those cases in which the intensity of this louder sound was itself varied there was added a third height of fall of two inches.  The succession of sounds was given, in different experiments, at rates of 2.5, 2.2, and 1.8 sec. for the whole series.  The durations of the intervals following and (in one or two cases) preceding the louder sound were changed; all the others remained constant.  A longer interval intervened between the close and beginning of the series than between pairs of successive sounds.  After hearing the series the subject reported the relations which appeared to him to obtain among its successive elements.  As a single hearing very commonly produced but a confused impression, due to what was reported as a condition of unpreparedness which made it impossible for the hearer to form any distinct judgment of such relations, and so defeated the object of the experiment, the method adopted was to repeat each series before asking for judgment.  The first succession of sounds then formed both a signal for the appearance of the second repetition and a reinforcement of the apperception of its material.