What have been described as periodicities, such as the daily variations of root-pressure, afford familiar instances of it.
It is mainly because these fisheries are seasonal that the periodicity has been noticed, and because of the economic interests involved the study of the seasonal and longer periodicities has become very important.
More and more the science seeks to discover periodicities and to correlate these with others.
Seasonal Periodicities of Life in the Sea.
Suppose now that F =a sin 22rn i t+b sin 21rn 2 t, the second term will evidently produce a series of combination tones of periodicities 2n 1, 2772, n, - n2, and n 1 -1-n 2, as in the first method.