Page:Great Neapolitan Earthquake of 1857 Vol 2.djvu/83

46 and$$r = \frac {(5.35 \times 0.827)}{0.757} = 5.84$$ geographical miles;

and for the vertical depth $$D$$ of the focus we have

or$$D = 5.64$$ geographical miles.

But this is below the true depth, as the focus is more to the westward, than in the right line joining the two towns as assumed, and were it worth while here, we might correct for this by a further trigonometrical operation.

Vietri is a tolerably well-built town, and does not present much antiquity in its edifices. Considering its proximity to the origin of the earthquake, it has escaped wonderfully, very few houses being actually fractured and thrown, though many fissured. It owes this in part, no doubt, to the steep emergence of the shock; but that alone would not account for it, nor for the difference in extent of injury, as compared with Auletta and Pertosa. Something in the deep formations, between it and the focus, or in the direction of the original impulse, has buffed the blow here. The frequent alternations, of clays and loose deposits, with the limestones, seem far too superficial, to account for the fact. The shock here, however, was severely felt; according to Signor Gorrosi it "fu ondulatoria e sussultoria e vorticosa e in tutti i sensi;" which is just what should be expected from so steep an emergence.

As to the character of the sound; he and the other "abitatori" agreed, "udite, grandi e subitano detonazioni nel lontano aere." They thought, the great shock and the awful subterranean and aerial thunder, came at the same