Occasionally the fluctuations of land may be exemplified to an extent which could hardly be expected, a fact well illustrated by the case of the Temple of Jupiter Serapis at Puzzuoli on the Bay of Naples. This temple, now in ruins, dates from a very ancient period, three marble pillars remaining to mark the extent of what was once a magnificent pile of buildings. Half-way up these pillars the marks of boring shell-fish are seen; some burrows formed by these molluscs still containing the shells by means of which they were excavated. At the present time, the sea-level is at the very base of the pillars, or exists even below that site. Hence arises the natural question--'How did the shell-fish gain access to the pillars, to burrow into them in the manner described?' Dismissing as an irrelevant and impossible idea that of the molluscs being able to ascend the dry pillars, two suppositions remain. Either the pillars and temple must have gone down to the sea through the subsidence of the land, or the sea must have come up to the pillars. If the latter theory be entertained, the sea-level must be regarded as having of necessity altered its level all along the Bay of Naples and along all the Mediterranean coasts. And as this inundation would have occurred within the historic period, we would expect not only to have had some record preserved to us of the calamity, but we should also have been able to point to distinct and ineffaceable traces of sea-action on the adjoining coasts. There is, however, no basis whatever for this supposition. No evidence is forthcoming that any such rise of the sea ever took place; and hence we are forced to conclude that the subsidence or sinking of the land contains the only rational explanation of the phenomena. We had thus a local sinking of land taking place at Puzzuoli. The old temple was gradually submerged; its pillars were buried beneath the waters of the sea, and the boring molluscs of the adjacent sea-bed fixed on the pillars as a habitation, and bored their way into the stone. Then a second geological change supervened. The action of subsidence was exchanged for one of elevation; and the temple and its pillars gradually arose from the sea, and attained their present level; whilst the stone-boring shell-fish were left to die in their homes. The surrounding neighbourhood--that of Vesuvius--is the scene of constant change and alteration in land-level; and the incident is worth recording, if only to shew how the observation of the apparently trifling labours of shell-fish serves to substantiate a grave and important chapter in the history of the earth.