dark lines; the main direction of the wave-path from Campostrina southwards is indicated by the large arrows w, w, and is that given generally by everything in the
piano, south of Polla, to Padula. But on the east side of the valley, going southward, it is constantly disturbed by the intermixture of another wave-path oblique to the former, and with increasing obliquity the further we go south; this intersecting angle, being small at Atena, greater at La Sala, and greater still at Padula, and the direction of wave transit of this secondary shock being always from N. E. to S. W., or from the lateral chain to the east of the valley.
It is obvious that the impulse given at the north end of the valley in a north to south direction, simultaneously to the deep clays of the piano, and to the eastern mountain range at its north end, was transmitted comparatively undisturbed as to direction through the former; but, in passing along the lateral ridge of limestone mountain across all the nearly vertical beds, transverse vibration was produced along
