On RYTHMICAL MEASURES. 59. 



tion that bears the name of poetry. la mufic, on the other 

 hand, a principal part of the pleafure to be communicated 

 muft depend upon the rythm ; and therefore in mufic other 

 proportions in duration, befides that of two to one, muft be 

 admitted. 



In order then that thefe proportions may be felt, and that 

 uniformity may be perceived amidft this variety, it is neceffary 

 that the duration of the fucceffive founds be regulated according 

 to fome fixed flandard or meafure, which may be obvious to 

 the hearer. This flandard muft be a determined portion of 

 time, of which every fou.nd muft be either an aliquot part or a 

 multiple. 



Time is a meafurable quantity, or may be confidered under 

 the ideas of equal, or of greater and lefs. Moft men are 

 capable of perceiving equal intervals of time, provided thofe 

 intervals do not exceed a certain magnitude. , When we hear a 

 number of fucceffive ftrokes, we can generally determine whe- 

 ther the intervals betwixt them are equal or unequal. We ac- 

 quire this idea of equal intervals of time, from the motion of 

 our own limbs, and of thofe of other animals, in walking or 

 flying, which nature, for the purpofes of eafe and grace, has 

 determined to be an uniform motion. We acquire the fame 

 idea from the movement of pendulums, and from the beating 

 of clocks and watches. By a habitual attention to thefe, men 

 come by degrees to have a very accurate perception of fmall 

 equal intervals of time. 



When we have fixed our attention upon any fuch interval, 

 and confider it as an unit of time, we can fuppofe it divided into 

 a certain number of equal parts ; and by motion we ad;ually 

 can make fuch a divifion. When we ftand befide a clock, we 

 can, with great eafe, make a certain number of uniform or 

 equal timed ftrokes in the intervals betwixt the feveral beats. 

 This power of divifion, however, has its limits. Although we 

 may conceive an interval to be divided into any number of 



H 2 equal 



