Page:Great Neapolitan Earthquake of 1857.djvu/403

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ITS FOlMATION--SMALL SLOPE. $19 of erosive deepening of the river at its north extremity; and for ages it must have remained a shallow and pro- bably' pestilential lake, of above 20 miles in length and 4 or 5 miles wide. The total difference of level now, between the water of the Calore at Polla and at the junc- tion of the Peglia with it at the extreme southern end, is said not to exceed 6 or 7 feet by Signor Palmieri of the Corps of Strade e Ponti, or only 3 inches to the mile. The marglnsd terrace round the plain contains numerous fragments of limestone, some angular, many more or less rounded. But the great clay central bed scarcely presents a pebble until high up towards the southern end of the valley, where the washings of the hill-side torrents disclose coarse gravel and boulders also, embedded in it. On the west side of the valley, I pass St. Arsenio and St. Pietro, both low-lying villages, placed upon the level of the marginal slope, that like a great shallow saucer, surrounds the plain. These towns have suffered but slightly, although not five miles in a right line from Polla, and St. Pietro, the more distant, has suffered the most. The damage done, how- ever, is almost confined to old houses, built of the usual sort of wretched, short, nobbly, bondless limestone rubble, of rounded lumps like irregular loaves, of from 6 to 16 inches diameter, with thick joints, of bad mortar, made of clay rather than sand; the general direction of wave- path from 142 �144 �of north. The character of the limestone of the mountains at both sides of the valley, begins rapidly to change, from that of the valley of the Tanagro and Salaris. It is no longer the hard, sharply-fracturing, clearly-bedded, and well-defined stone of the latter, but a loose, irregular, ill-defined, and Digitized by Googlc