The full rôle played by Rhythm in the economy of nature is still wrapt in mystery. We may, however, surmise that further research will probably prove that it is the basis of all development and growth, and one of the principal mainsprings of the universe. We already know something, on the one hand, of cosmic rhythm, and the rhythm of the seasons, while on the other, the study of biological science is bringing to light the importance of rhythm as a factor in the life of all organisms. An application of this is found in modem studiesof industrial problems. That rhythm plays a large part in preventing fatigue is well known to anyone who has walked to the accompaniment of a band, but the idea that in mechanical work the rhythm of the machine must be fixed to suit that of the operator is new. Research on the physiological rhythmic changes in the body during the day has resulted in the discovery of the best relative times of work and rest, the relation between output and fatigue, etc. 1 We are but at the beginning of such research and later results may establish the fact that the consideration of the physiological rhythm of the human organism may be one of the foremost questions of industrial efficiency. The most primitive type of rhythmic movement, the dance, was, it is believed, the earliest known form of artistic development. It is not confined to the human race ; examples of it are well known amongst animals and birds. The origin of the dance is unknown—probably in its original form it is the outcome of the desire to express some strong emotion by movement of the body. It is difficult to realize that dancing as an outlet of emotion is prior to music, that in fact, the first music was composed or extemporized in order to accompany dancing, for from the earliest times there has been some attempt at a rhythmic accompaniment, thus bringing into play the two factors of rhythm and sound. From these early attempts we may trace the evolution of all rhythmic music. Dancing in some form seems to have been in existence at the time of the earliest records of man known. It certainly appears to have been the most primitive means for man to express his strong emotions. Of the earliest ceremonial dances three main types can be traced :

(1)Religious dances, imitating the movement of the spheres.

(2) Dramatic dances, representing strong emotional states, such as love, joy, hate.

(3) Dances involving the mimicry of animals.