The holes drilled by the patient lithodomus, as I have said, do not extend through the whole height of the column, but have a range of about nine feet only, which is thus the measure of the space left for the operations of the busy spoiler. Above the ring of perforations one sees the indications of ordinary weathering, so that the upper edge of the holes doubtless marks the level of high water, and the summit of the columns stood up above the waves. But one does not see readily what protected the lower portion of the marble. Possibly, before the land swayed downwards something fell which covered them. In the twelfth century the Solfatara broke forth into eruption for the last time. The scoriæ and stones fell thick in Pozzuoli, and they filled the court of the Serapeon to the height of some twelve feet. Probably the sea had then already stolen into the courtyard; and it may be that the earthquakes attending the eruption caused the subsidence which left the lithodomus free to crawl and bore upon the stones which saw the ancient mysteries of Serapis. At any rate it was another volcanic outburst which raised the dripping columns from the sea in 1538, since which time the land has been swaying slowly down once more, so that now if anyone cares to scratch the gravel in the courtyard he will find he has constructed a pool of clear sea water. It is a strange and terrible thing to realise the existence of hidden forces which can sway the solid earth as lightly as a puff of wind disturbs an awning; none the less terrible because the ground has risen and fallen so very gently that the pillars stand erect upon their bases. Once more, as at the Solfatara, one has the sense of treading over some vast chasm filled with a sleeping power which may awake at any moment. Let us go on beyond the city and see what has happened elsewhere upon this bay, so beautiful and yet so deadly, a strange dwelling-place for men who have but one life to pass on the surface of this earth.