The greatest of these musical festivals directly precedes the mating season, and is a dramatic instance of a manifestation of an inner rhythm which corresponds to an external periodicity.
"The Human Side of Animals"
Royal Dixon
It is this life-like periodicity in the geyser's mode of action which makes it as awe-inspiring to behold as it is puzzling to explain.
"A Girl's Ride in Iceland"
Ethel Brilliana Alec-Tweedie
Yet the periodicity of a geyser's action cannot be said to be entirely due to volcanic agency.
"A Girl's Ride in Iceland"
Ethel Brilliana Alec-Tweedie