In the first experiment of this group the reactor was asked to tap out a series in which temporal, but not intensive variations were introduced; the strokes were to be of uniform strength but separated into groups of two beats.  No directions as to length of pause between the successive groups were given, but the whole form of the groups was to be kept absolutely constant.  The reports of the subjects were uniformly to the effect that no accent had been introduced.  At a cursory examination no intensive grouping was apparent.  These records were the earliest analyzed, when only time relations were in mind, and no measurements were made of variations in strength.  Only the mean variations of the intervals, therefore, will here be taken up.

A word first as to the relative value of the two intervals and its significance.  The form of a rhythmical series is determined in every part by subordination to principles of strict temporal arrangement.  Every suppression of elements in such a series, every rest and syncopated measure has as positive and well-defined a function as have the successive reactions and their normal intervals.  If such a pause is made as we find introduced in the present case, its value must be a fixed function of the system of durations of which it forms a part, whether it replace an element in a rhythmical unit, or a subgroup in a higher rhythmical quantity.  In general, the value of such a rest is less than the duration of a corresponding full measure or interval.  For example, the syncopated forms | >q % | and | >q % %_| are demonstrably of shorter average duration than the corresponding measures| >q q | and | >q q q_|; and the pause occurring at the close of a syncopated line—­such as that in the middle of a catalectic trochaic tetrameter—­should be found of less value than that of the regular foot.

In the present instance two reactions are made, a pause follows, then the reactions take place again, and so on.  The intervals separating successive groups of reactions thus result from the coalescence of two periods, the interval which would regularly follow the reaction and the additional pause at its close.  The value of the latter I interpret as functionally equivalent to a group of two beats and not to a single interval; that is, the rhythm beaten out is essentially quadruple, the second member of each composite group being suppressed, as follows: 
    >
  | q q; % % |.
    \______/

To estimate the proper value of such a rest the average relative duration of first and second intervals was taken in a continuous series of two-beat measures, in which the first member was accented sufficiently to define the rhythmical groups.  The ratio was 1.000:0.760.  In the present instance the values of the simple initial interval and the composite interval which follows it are, in terms of the linear measurement, 1.55 mm. and 3.96 mm.  Assuming the above ratio to hold, the duration of a period which included the