objected, that the adjoining ruins of the Temples of Neptune, and of the Nymphs, are some feet under water, and that the arches of the so-called Mole of Pozzuoli, are covered above the level of the springings. The levels of these two latter temples will not accord either with the presumed depression or elevation of Serapis, and may hence be made to argue as much against, as for the oscillatory view; and as to the arches and general structure, of the so-called mole now deeply immersed, I am satisfied that it never was built for a sea mole at all, and that the whole of the arches were originally built on dry land, and for other purposes. It would be a work of no small difficulty, to construct these piers and arches in the open sea-way, where their remains now stand, with all the aids that modern engineering afford: and without the diving-bell we may safely affirm that they never could have been built in open sea-water. They, further, are of dimensions and construction, that no Roman or any other architect would have adopted for a marine mole.
How, then, came they immersed as they are? It appears to me that they, and the incoherent tufaceous land, that sustains them and these temples, are now, and have long been, in gradual process of insensible land-slip downward and seaward, by the continual removal by tidal action of the loose material, from the foot of the submarine talus, which the soundings prove, to be outside them, in the roadstead, hence unequal subsidence, but always greatest where nearest the sea-shore. And this view is strongly corroborated by the fact, that all the standing columns at Serapis lean some inches out of plumb to seaward, and that the whole floor of the place is waved and uneven, and with a general out-
