ayoralty, had succeeded in perforating the five leagues of sewer which existed previous to 1806.
All sorts of obstacles hindered this operation, some peculiar to the soil, others inherent in the very prejudices of the laborious population of Paris.
Paris is built upon a soil which is singularly rebellious to the pick, the hoe, the bore, and to human manipulation.
There is nothing more difficult to pierce and to penetrate than the geological formation upon which is superposed the marvellous historical formation called Paris; as soon as work in any form whatsoever is begun and adventures upon this stretch of alluvium, subterranean resistances abound. There are liquid clays, springs, hard rocks, and those soft and deep quagmires which special science calls moutardes.[59] The pick advances laboriously through the calcareous layers alternating with very slender threads of clay, and schistose beds in plates incrusted with oyster-shells, the contemporaries of the pre-Adamite oceans.
Sometimes a rivulet suddenly bursts through a vault that has been begun, and inundates the laborers; or a layer of marl is laid bare, and rolls down with the fury of a cataract, breaking the stoutest supporting beams like glass.
Quite recently, at Villette, when it became necessary to pass the collecting sewer under the Saint-Martin canal without interrupting navigation or emptying the canal, a fissure appeared in the basin of the canal, water suddenly became abundant in the subterranean tunnel, which was beyond the power of the pumping engines; it was necessary to send a diver to explore the fissure which had been made in the narrow entrance of the grand basin, and it was not without great difficulty that it was stopped up.