The females produce thousands of larvae, which circulate in the blood, and show a certain periodicity in their appearance, being much more numerous in the blood at night than during the day.
The periodicity of the seasons usually allows two, and sometimes three, harvests in the year, but not necessarily, nor indeed usually, from the same fields.
He found out the formula for deriving the sine of a multiple angle, knowing that of the simple angle with due regard to the periodicity of sines.
The principle of the periodicity of the councils was admitted; the first was to assemble after the lapse of five years, the second within the next seven years, and subsequent councils were to meet decennially.
John Goodricke established in 1782 the periodicity of its change in about 2 d 21 h, and suggested their cause in recurring eclipses by a large dark satellite.
The surface level of the lake varies with the season, and recent observations taken on behalf of the Palestine Exploration Fund seem to show that there are probably cyclical variations also (ultimately dependent on the rainfall), the nature and periodicity of which there are as yet no sufficient data to determine.
Formerly it was generally supposed that the Tartini tone was due to the beats themselves, that the mere variation in the amplitude was equivalent, as far as the ear is concerned, to a superposition on the two original tones of a smooth sine displacement of the same periodicity as that variation.
In this case there is approximate periodicity in the half interval, but complete periodicity only after the whole interval.
The periodicity shows itself in the form of an exacerbation of the still continuing fever, and that exacerbation may take place twentyfour hours after the first onset, or the interval may be only half that period, or it may be double.
There is no doubt about the latter variation, but with regard to its periodicity - that is, the number of years elapsing between one maximum and the next - much still remains to be done.