CHAPTER IV.
OF THE EFFECTS OF THE PHYSICAL CONFIGURATION OF THE SURFACE, AND THE FORMATION BENEATH IT, UPON THE PROGRESS OF THE WAVE.
That is to say, upon the distance of its sensible transmission, and irrespective of local or other conditions, changing its direction, or producing reflection and refraction, which will require separate consideration.
The conditions in nature that are most effective and frequent in modifying the distance of transmission of the wave, in formations of the same, or nearly the same materials, are—
2nd. The occurrence of great faults, or lines of dislocation, whether parallel or transverse, to the great chains, filled with loose, or with heterogeneous material, and their direction with regard to the origin, &c., as before.
3rd. The existence of deep and continuous valleys, narrow in character, and with precipitous flanks, and their direction with regard to the origin, &c.
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