TABLE LXX.

  Stress.  Interval I. Interval II.  Interval III. 
  Initial, 5.82 per cent. 6.45 per cent. 4.65 per cent. 
  Median, 9.95 " 7.87 " 4.70 "
  Final, 11.95 " 9.77 " 7.15 "

The relation holds in all cases except that of I. to II. in the rhythm with initial stress.  From this table may be gathered the predominance of primacy of position as a factor of disturbance over that of stress.  Indeed, in this group of reactions the index of variation for the accented element, all forms combined, falls below that of the unaccented in the ratio 6.95 per cent. :  7.91 per cent.

In rhythms of four beats, as in those of three, the estimation of values is made on the basis of an average of the mean variations for the three intra-group intervals, which is then compared with the final or inter-group interval.  As in those previous forms, sensitiveness to variations in duration is greater throughout in the case of the latter than in that of the former.  The proportional values of their several mean variations are given in the annexed table: 

TABLE LXXI.

Interval.   Initial Stress.  Secondary Stress.  Tertiary Stress.  Final Stress. 
Intra-group,    1.000           1.000            1.000           1.000
Inter-group,    0.941           0.775            0.725           0.713

This relation, true of the average of all intra-group intervals, is not, as in the preceding forms, true of each of the three constituent intervals in every case.  In the second and fourth forms, those marked by secondary and final stress, it holds for each member of the group of intervals; in the first form it fails for the second and third intervals, while in the third form it fails for the last of the three.

The proportional amount of this difference in mean variation continuously increases from beginning to end of the series of rhythmical forms.  This cannot be interpreted as directly indicative of a corresponding change in the definition which the four forms possess.  The absolute values of the several mean variations must simultaneously be taken into account.  First, then, in regard to the final pause there is presented the following series of values: 

TABLE LXXII.

Stress.  Initial.        Secondary.      Tertiary.       Final. 
M.V.    6.57 per cent. 9.50 per cent. 4.90 per cent. 15.70 per cent.

A very striking rhythmical alternation in the magnitude of the mean variation thus occurs according as the accents fall on the first member of the subgroups when its amount is smaller or on the second member when it is larger.  Further, the cases noted above, the second and fourth forms, in which each of the intra-group intervals is severally of greater mean variation than the final pause, are just those in which the index of mean variation in the final pause itself is at a maximum.