nodal extrasystole

The mode of vibration of the disc is indicated by the sand accumulating along the lines of least vibration, called nodal lines.

The Nodal brothers' Relacion, which they seem to have been following, mentions, p. 37 vo.

It was in 1618-19 that the observations of Nodal first gave the easterly bend to the southern extremity of the continent.

These nodal points will not, however, afford a general explanation of the many-branched radiants.