In the ruins of the ancient temple of Jupiter Serapis are three marble monoliths 40 feet in height, curiously marked by a roughened surface between the heights of 12 and 21 feet above their pedestals (Fig. 285). Closer inspection shows that this roughened surface has been produced by a marine, rock-boring mollusk, the _lithodomus_, which lives in the waters of the Bay of Naples, and the shells of this animal are still to be found within the cavities upon the surface of the columns. Without recounting details which have been many times recited since these interesting monuments were first geologically explored by Babbage and Lyell, it may be stated that a record is here preserved, first of subsidence amounting to some 40 feet, and of subsequent elevation, of the low coast land on which stood the temple in the old Roman city of Puteoli (Fig. 286). At the time of deepest submergence the top of the lithodomus zone upon the column stood at the level of the water in the Bay of Naples, the smoother lower zone being buried at the time in the sand at the bottom, and thus made inaccessible for the lithodomi. It is to be added that studies made in the environs of Pozzuoli have fully confirmed the changes of level revealed by the columns, through the discovery of now elevated shore lines which are referable to the period of deep submergence. =Simultaneous contrary movements upon a coast.=—In our study of the changes in the level of the ground that take place during earthquakes, it was learned that neighboring sections of the earth’s crust may be moved at different rates or even in opposite directions, notwithstanding the fact that the general movement of the province is one of uplift. Thus during the Alaskan earthquake of 1899, although portions of the coast line were elevated by as much as forty-seven feet, neighboring sections were raised by smaller amounts, and some small sections were sunk and so far submerged that the salt water and the beach sand were washed about the roots of forest trees. [Illustration: FIG. 286.—Pozzuoli in the 3rd, 9th, and 20th Centuries.]