Page:Great Neapolitan Earthquake of 1857.djvu/406

322 what I could not at the time discover. At about 2 miles south of Polla, and at a point of the road about the general level of the central plain here, I took by barometer the level of the Vallone. At 1h 20 Greenwich time (14th Feb.) barom. reads 29.6 inches, thermo. 62°, which, reduced, gives 581.5 feet for the level of the central plain above the sea. Either by misreading, or through some great inequality of atmospheric pressure on this day, between Naples and the Vallone, this observation is certainly about 100 feet below the truth; for the bed of the Tanagro at Auletta was ascertained to be 576 feet above the sea. The waters, issuing slowly from St. Michael's cavern, are about 80 feet above the river beneath, and there is probably 20 feet fall between Perrosa and Auletta; while it is probable that the fall in the rocky tube is but a few inches between the water at Polla and its issue at the cavern. There must therefore be a fall between Polla and Auletta of about a hundred feet. We may therefore take the mean level of the Vallone di Diano at about 700 feet above the sea, and the barrier of Campostrino, before its fracture, stood 1,363 feet above the plain. This was the depth of the ancient lake or arm of the sea.

While at Auletta, the gendarmes and others there, had affirmed that on the night of the earthquake, they had seen some unusual sort of light in the sky or air, and some of them said that it appeared to come up out of the earth. At the moment, I looked upon this as a superstitious tale; the rather, as Padre Mancini had not remarked it; but I find almost every one I converse with in these districts, speaks of having seen some unusual halo-like light in the