At the period of the formation of the lowest bed of coal, the level of the carboniferous continent would seem to have been the highest; for when the stratum of bituminous matter had accumulated to the depth of a few feet, it was submerged by water, that brought shales and sandstone, and spread them in layers of many feet in thickness above it, before the requisite conditions were reached for the formation of another stratum. The intervals of repose, when the surface of the land was nearly at a level with the sea, were marked by the carbonaceous matter, and the thickness of each stratum measures the length of time during which this state of quiescence continued.

The changes of level were apparently all in one direction, that of submergence. During the epoch of the coal measure, the surface of the land and at the sea level, while the first stratum of coal was forming, was depressed until there had been deposited upon it a series of strata, which measured in Ohio, before being eroded, fully 2,000 feet in thickness, and included at least twelve workable seams of coal, with a great number of thinner ones.

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Water Works Weather Chart for 1880
From Signal Service Records

At the time of the formation of the highest coal-beds, the Alleghany Mountain system was elevated, and an area including most of the States of our Union was raised above the ocean, never again, to the present time, submerged. The anthracite coal basins of Pennsylvania were once a part of the Alleghany coal-field, but were isolated by the upheaval and erosion of the mountain ridges; and by this disturbance, all the rocks were more or less metamorphosed, and most of the volatile ingredients of the coal driven off, leaving it in the condition of anthracite.

THE DEPOSITS OF DRIFT.

The period immediately following the Tertiary age [but separated from it by we know not how many years] presents a complete change in the physical condition, that during this time the pervading warmth of the Tertiary was changed to an Arctic cold. While, in the former age, the climate of our Southern States was carried to Greenland; in the latter, or drift period, the present Greenland was brought as far south as the Ohio. This was when we had our icebergs or glacial age. The gravel, the bowlders, and an unstratified clay thickly studded with small fragments of rock, are the glacial surface-covering. Mingled with these are found many pebbles and bowlders of crystalline rock, such as are found north of the great lakes.

The finding of large bowlders in fields are the deposit of icebergs that once floated over our country. The glaziers reached as far as Cincinnati, planing, grinding down, smoothing all rock surfaces, and excavating the basins of our great lakes. The retreat of the glaciers left clay and bowlders and a great inland sea of fresh water, filling basins, before occupied by ice, 500 feet above the present surface of Lake Erie. At a later period, by continental elevation or the removal of barriers to drainage, the water level was gradually depressed until the inland sea was reduced to the comparative insignificance of our great lakes.

The descent of the water by motion of the waves, cut the well-marked terraces and edges.