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 about fifteen feet below the pavement of the city. How life is sustained in this subterranean world of infusoria is a mystery, since it is evident that the organisms cannot come in contact with any air except that which is contained in the water which percolates through the mass.

This discovery was followed by others equally astounding. A mass, more than twenty feet in thickness, of light silicious earth, was found at Ebsdorf, in Hanover, and, on examination by the microscope, it appeared that this earth consisted entirely of the minute shields of invisible infusoria. Again, the beds of silicious marls upon which the towns of Richmond and Petersburg, in Virginia, are built, are now known to be almost wholly made up of the skeletons of diatomacæeDiatomaceæ [sic]. The forms that predominate are elegant saucer-shaped shields, elaborately ornamented with hexagonal spots disposed in curves, and resembling the engine-turned sculpturing on a watch. They vary in size from the one-hundredth to the one-thousandth of an inch in diameter.

We need not carry our microscope out of England to discover the remains of infusoria in the earth's crust. The white chalk which underlies or forms the surface of the south-eastern part of England, is a mere aggregation of microscopic shell and corals, so minute that upwards of a million of the former are contained in a single cubic inch of this