In the Middle Ages, when an edifice was complete, there was almost as much of it in the earth as above it. Unless built upon piles, like Notre-Dame, a palace, a fortress, a church, had always a double bottom. In cathedrals, it was, in some sort, another subterranean cathedral, low, dark, mysterious, blind, and mute, under the upper nave which was overflowing with light and reverberating with organs and bells day and night. Sometimes it was a sepulchre. In palaces, in fortresses, it was a prison, sometimes a sepulchre also, sometimes both together.

These mighty buildings, whose mode of formation and vegetation we have elsewhere explained, had not simply foundations, but, so to speak, roots which ran branching through the soil in chambers, galleries, and staircases, like the construction above. Thus churches, palaces,