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.