1. Two years ago, in a lecture entitled “On Elastic Surface Waves”, the author tried to give the definition of surface waves as follows:
“When waves are propagated in a medium with a single boundary or several parallel boundaries and their wave-front is perpendicular to the boundary surface, we call them surface waves.”
2. This is, however, somewhat unsatisfactory, and the author would here like to add the following conditions.
1) All the media are bounded (with respect to the z-direction), or 2) Waves in the semi-infinite part assume the [E]-type.
3. The existence and other properties of surface waves corresponding to each symbolical representation were considered individually. Thus the problem of the existence of waves with one or two-phase-type is solved completely.
