Jean Valjean found himself in the presence of a fontis.

This sort of quagmire was common at that period in the subsoil of the Champs-Élysées, difficult to handle in the hydraulic works and a bad preservative of the subterranean constructions, on account of its excessive fluidity. This fluidity exceeds even the inconsistency of the sands of the Quartier Saint-Georges, which could only be conquered by a stone construction on a concrete foundation, and the clayey strata, infected with gas, of the Quartier des Martyrs, which are so liquid that the only way in which a passage was effected under the gallery des Martyrs was by means of a cast-iron pipe. When, in 1836, the old stone sewer beneath the Faubourg Saint-Honoré, in which we now see Jean Valjean, was demolished for the purpose of reconstructing it, the quicksand, which forms the subsoil of the Champs-Élysées as far as the Seine, presented such an obstacle, that the operation lasted nearly six months, to the great clamor of the dwellers on the riverside, particularly those who had hotels and carriages. The work was more than unhealthy; it was dangerous. It is true that they had four months and a half of rain, and three floods of the Seine.