Page:Great Neapolitan Earthquake of 1857 Vol 2.djvu/329

264 of position of the particles, of the incoherent formations at the slope of the rock, at $$a\ b$$, (Fig. 344); nearly as if the sur-

face of contact, was with respect to the loose material, a free lying surface. The same will be the case at the emergent side of the range, $$c$$ to $$d$$, in converse order, for such portion of the wave, as at greater depth may have directly entered and passed through, the central rocky mass between $$a$$ and $$d$$; there will, therefore, be in such a case, almost a complete extinction of the wave.

The former case, that of Fig. 343, is mentioned as amongst the conditions which modified the great Carpathian shock, of Sillein, in Hungary, of 16th January, 1858, so well described by Herr Jeitteles, of Kaschau; (Sitzungbericht der Mat. Naturw. Classe der Kaisere 'Akadee' Bande xxxv., s. 511,) and the latter has been already described where occurring locally in having cut off the town of Diano, from the shock, from north to south through the piano. (Part II, p. 330.)

The occurrence of the second condition, viz., great lines of dislocation where the fissure first opened, has to a great depth and for a considerable thickness, become filled in with loose material,—seems, from the results of my observations on this earthquake, to be competent to arrest at once almost the whole progress of the wave.

Its entire volume, or by far the greater portion that arrives at the first surface of contact, or wall of the filled