ilar ideas with certain
intervals of time, or distances of space between them, is attended
with agreeable sensations, besides that simply of perception; and,
though it appears to be diametrically opposite to the pleasure arising
from the novelty of objects above treated of, enters into the
compositions of all the agreeable arts.

The pleasure arising from the repetition of similar ideas with certain
intervals of time or distances of space between them is a subject of
great metaphysical curiosity, as well as the source of the pleasure
derived from novelty, which will I hope excuse its introduction in
this place.

The repetitions of motions may be at first produced either by
volition, or by sensation, or by irritation, but they soon become
easier to perform than any other kinds of action, because they soon
become associated together; and thus their frequency of repetition, if
as much sensorial power be produced during every reiteration, as is
expended, adds to the facility of their production.

If a stimulus be repeated at uniform intervals of time, the action,
whether of our muscles or organs of sense, is produced with still
greater facility or energy; because the sensorial power of
association, mentioned above, is combined with the sensorial power of
irritation; that is in common language, the acquired habit assists the
power of the stimulus.

This not only obtains in the annual, lunar, and diurnal catenations of
animal motions, as explained in Zoonomia, Sect. XXXVI. which are thus
performed with great facility and energy; but in every less circle of
actions or ideas, as in the burden of a song, or the reiterations of a
dance. To the facility and distinctness, with which we hear sounds at
repeated intervals, we owe the pleasure, which we receive from musical
time, and from poetic time, as described in Botanic Garden, V. II.
Interlude III. And to this the pleasure we receive from the rhimes and
alliterations of modern versification; the source of which without
this key would be difficult to discover.

There is no variety of notes referable to the gamut in the beating of
a drum, yet if it be performed in musical time, it is agreeable to our
ears; and therefore this pleasurable sensation must be owing to the
repetition of the divisions of the sounds at certain intervals of
time, or musical bars. Whether these times or bars are distinguished
by a pause, or by an emphasis, or accent, certain it is, that this
distincti