Everywhere else the sepulchre is sinister; here it is deformed.
The depth of the fontis varied, as well as their length and their density, according to the more or less bad quality of the subsoil. Sometimes a fontis was three or four feet deep, sometimes eight or ten; sometimes the bottom was unfathomable. Here the mire was almost solid, there almost liquid. In the Lunière fontis, it would have taken a man a day to disappear, while he would have been devoured in five minutes by the Philippeaux slough. The mire bears up more or less, according to its density. A child can escape where a man will perish. The first law of safety is to get rid of every sort of load. Every sewerman who felt the ground giving way beneath him began by flinging away his sack of tools, or his back-basket, or his hod.
The fontis were due to different causes: the friability of the soil; some landslip at a depth beyond the reach of man; the violent summer rains; the incessant flooding of winter; long, drizzling showers. Sometimes the weight of the surrounding houses on a marly or sandy soil forced out the vaults of the subterranean galleries and caused them to bend aside, or it chanced that a flooring vault burst and split under this crushing thrust. In this manner, the heaping up of the Parthenon, obliterated, a century ago, a portion of the vaults of Saint-Geneviève hill. When a sewer was broken in under the pressure of the houses, the mischief was sometimes betrayed in the street above by a sort of space, like the teeth of a saw,