CHAPTER XI.
OF THE ACTUAL DIMENSIONS, FORM, AND SUBTERRANEOUS POSITION OF THE FOCAL CAVITY, AS DEDUCED.
From all that has preceded, in relation to 1st, the form of the isoseismals; 2nd, the horizontal spread, from convergence of the wave-paths, to a small focal area; 3rd, the nature of the sounds heard, at dififerent points, round the focus; and 4th, the tremulous movements; we are enabled to assign, with a very high degree of probability as to correctness, the size, form, and position, of the focal cavity itself.
We have found that (Chap. II.) the vertical dimension of this cavity, could not have exceeded about 5·3 miles, but was most probably limited, to 3 geographical miles. We have also found (Chap. I.) the preponderating numbers of our wave-paths, fall to within an horizoutal length of 5 geographical miles, 212 at either side the focal point. But to the south of this point, we have six wave-paths, (of which five, are nearly parallel, to the major axis, of the meizoseismal and to each other,) which fall, rather above 2 geographical miles, more to the southward, of the 212 mile circle; viz., those of, Marsica Nuovo, Saponara and its Piano, Tramutola, and Spinosa. These point distinctly to a prolongation of the focal cavity, towards the south and west, to an extent approximately equal to the transverse range of
