302 THEORETICAL BIOLOGY 



Now the sound-sequence in a melody is also the expression 

 of a law, for which we have no exact word. It is true that, 

 in a general way, we speak of the relationship of the sounds ; 

 but for the special law determining the sound-sequence in a 

 certain tune, we have no expression. In this case also we 

 help ourselves out with the word rhythm, although that is 

 intended to describe the special law of beat-sequence. 



But it is necessary to distinguish between the two. 

 Accordingly I shall describe the law displayed in the sound- 

 sequence as rhythm, and that displayed in the beat-sequence 

 as " beat-rhythm." 



In melody the conditions are extraordinarily clear : the 

 sounds are arranged in a fixed relation, which in all circum- 

 stances must be preserved, if no dissonance is to come in. 

 The rhythm of the single sound-sequences, however, cannot 

 be derived from this relation, which has been compared 

 to a seven-sided column, for the law of that relation tells us 

 nothing, for instance, as to whether two related notes are to 

 sound simultaneously or in succession. 



The law of relationship deals only with the special nature 

 of the sounds and how they are adapted to one another. 

 The rhythm should reproduce the law according to which 

 the peculiarity is made use of in single instances. 



The shape and material properties of the bricks reproduce 

 the peculiar nature of the structural material of a house, 

 and the laws of this must be kept in mind in building. The 

 sequence of construction that causes the house to arise, and 

 with which brick after brick is harmonised in accordance 

 with its special nature — that is the rhythm. 



In the development of any structure the same thing 

 can be demonstrated — namely, elementary parts, which 

 are adapted to one another in accordance with their special 

 nature, and a rule, the rhythm, by which the structure arises. 

 The law of peculiarities is called in chemistry the affinity of 



