As the reader sees, the subterranean labyrinth of Paris is today more than ten times what it was at the beginning of the century. It is difficult to form any idea of all the perseverance and the efforts which have been required to bring this cesspool to the point of relative perfection in which it now is. It was with great difficulty that the ancient monarchical provostship and, during the last ten years of the eighteenth century, the revolutionary mayoralty, 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