[60] Here a word of caution is needed. It will be observed that the
regularly balanced line of the classical couplet requires not only a
medial pause, but also a pause at the end. Hence where we find, as in
the verse of Keats, a large number of medial cesuras but at the same
time a very large number of "run-on" lines, the characteristic effect of
the medial pause is almost entirely lost, and the number of medial
pauses is not significant.
[61] This combination (of pyrrhic and spondee) is of course very
frequent; and where both substitutions occur together, the general
average of accents is maintained, only with exchange of position. On the
other hand, where there appears a large number of pyrrhics with almost
no spondees (as in the case of Dryden), a different sort of verse is
indicated,--one where the lines gain a certain lightness and rapidity
from the lack of the full number of fully accented syllables.
[62] "Divination by Statistics," in the _Atlantic Monthly_, January,
1902.