Another cause of the unhealthiness of Munich is the nature of the soil. The ground upon which the city is built, as also the land for a considerable distance round about, was formerly the bed of a lake, and consists of a loose gravel to the depth of many feet, there being scarcely enough earth upon the top to furnish subsistence for the commonest grass and weeds, while trees, esculent vegetables and flowers can only be raised by preparing a new soil, which must be continually enriched by artificial means. A proverb says, "Scratch a Russian and the Tartar shows through;" so one has only to stir the soil of Munich to find just below the surface the coarse gravel, defying cultivation. Of course, all the fluid matter deposited upon the surface that does not exhale in the atmosphere percolates through this loose stratum until it reaches the rock, where it stagnates and corrupts, returning into the air in the form of poisonous gases, instead of undergoing the healthy transformation which is effected in all soils capable of sustaining vegetable life. If the fluid thus held in solution were only the rain from heaven, the result would not be so disastrous; but, unfortunately, there is scarcely any kind of filth that is not allowed to contribute constantly to the subterranean supply of moisture. It has been estimated that of the seventy-five thousand tons of refuse matter which Munich furnishes within a year, scarcely one-third is carried out of the city: the rest is suffered to go into the ground upon the spot. Nor can that third which is gathered up be considered as taken out of harm's way, since all of it that can be regarded as manure is spread at once upon the neighboring fields, whence it sends back its stenches upon every wind that blows.