the time form is fundamental.  Through all variations its equivalences must be adhered to.  Stress makes rhythm only when its recurrence is at regular intervals.  The number of subordinate factors which combine with the accented element to make the group is quite indifferent.  But whether few or many, or whether that element on which stress falls stands alone (as it may), the total time values of the successive groups must be sensibly equivalent.  When a secondary element is absent its place must be supplied by a rest of equivalent time-value.  If these proper temporal conditions be not observed no device of intensive accentuation will avail to produce the impression of metrical equivalence among the successive groups.

B. The Distribution of Elements Within the Group.

(a) The Distribution of Intensities.

In the analysis of the internal constitution of the rhythmic unit, as in other parts of this work, the investigation follows two distinct lines, involving the relations of rhythm as apprehended, on the one hand, and the relations of rhythm as expressed, on the other; the results in the two cases will be presented separately.  A word as to the method of presentation is necessary.  The fact that in connection with each experiment a group of questions was answered gives rise to some difficulty in planning the statement of results.  It is a simple matter to describe a particular set of experiments and to tell all the facts which were learned from them; but it is not logical, since one observation may have concerned the number of elements in the rhythmic unit, another their internal distribution, and a third their coalescence in a higher unity.  On the other hand, the statement of each of these in its own proper connection would necessitate the repetition of some description, however meager, of the conditions of experimentation in connection with each item.  For economy’s sake, therefore, a compromise has been made between reporting results according to distribution of material and according to distribution of topics.  The evidence of higher grouping, for example, which is afforded by variations in duration and phases of intensity in alternate measures, will be found appended to the sections on these respective classes of material.

In all the following sections the hammer-clang apparatus formed the mechanism of experimentation in sensory rhythms, while in reactive rhythms simple finger-tapping was employed.

In comparing the variations in stress which the rhythmical material presents, the average intensities of reaction for the whole group has been computed, as well as the intensities of the single reactions which compose it.  This has been done chiefly in view of the unstable intensive configuration of the group and the small amount of material on which the figures are based.  The term is relative; in ascertaining the relations of intensity among the several members of the group, at least ten successive repetitions,