Experiments and theory of undulatory locomotion in a simple structured medium.
From the sciencedaily.com
The explanation is probably to be sought in those phenomena which have given rise to the theory of action at a distance, and in the properties of light which have led to the undulatory theory.
From the froarty.scienceblog.com
But therewith the conception of the ether has again acquired an intelligible content, although this content differs widely from that of the ether of the mechanical undulatory theory of light.