The basin containing the coals, as defined above, is inclosed within the great chains of primary and secondary mountains of the central district of Scotland, which were upheaved into dry land before the coal-measures were formed. A period of violent disturbance had thus passed away, when the carboniferous formation bears evident tokens of having been begun and completed in tranquil waters. But after being collected, the coal-metals were exposed to the action of disturbing forces: eruptive masses, of igneous origin, have invaded their domain; basalts and greenstone, trap dykes and veins, are everywhere found within their inclosure; and apparently the utmost disorder and irregularity now reign, where order and stillness once prevailed. But look a little closer: examine the length and breadth of any coal-field in any part of the world, and you will discern proofs of a purpose, not only in the quality of their materials, but in the position, arrangement, and grouping of the metals; those very disturbing forces, to which they and all earthly things have been exposed, giving unequivocal testimony of an overruling intelligence continuing, through all ages, to superintend and guide their various operations. Study any coal-field in your neighborhood, and observe _the place_ of the mineral. It does not lie exposed upon the surface, but is placed at a considerable depth in the earth; of which many are apt to complain, thinking that, if a different arrangement had prevailed, much needless labor and expense would have been saved. But the constituent elements of coal are such, that by exposure on the surface the mineral would, in a comparatively short period of time, have run to waste and decay. Even a thick covering of earthy mold would not have been sufficient to protect it; and therefore was the treasure purposely hid in the earth, and so inclosed that the floods could not wash it away. Then consider the _quality_ of the rocks by which the coal is protected, and along with which it is invariably associated. These consist of limestone, sandstone, shale, and clay ironstone, which always occupy the same basins, and alternate with the coal sometimes in a series of more than a hundred beds. Such a group of well-characterized rocks not only act as a guide for determining the localities of the valuable mineral, but they serve the double purpose of facilitating the excavation, by affording at once a safe roofing to the mine, and an easy passage for the drainage of the water which accumulates in the pits. No other class of rocks would have been so suitable. The granite and crystalline rocks would have been inconvenient, or wholly unfit: no borings could have been effected through such materials to any extent; the operations underneath would have been equally difficult and unmanageable; and through such hard compact substances the drainage must have been impracticable. But a still more remarkable indication of contrivance arises from _the elevated_