Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/398

 394 depths, wherein they were formed; and it required the exercise of some of the most powerful machinery in the Dynamics of the terrestrial globe, to effect the changes that were requisite to render these Elements of Art and Industry accessible to the labour and ingenuity of man. Let us briefly examine the results that have been accomplished.

The place of the great Coal formation, in relation to the other series of strata, is shown in our first section (Pl. l. Fig. 14.) This ideal section represents an Example of dispositions which are repeated over various areas upon the crust of the Globe.

The surface of the Earth is found to be covered with a series of irregular depressions or Basins, divided from one another, and sometimes wholly surrounded by projecting portions of subjacent strata, or by unstratified crystalline rocks, which have been raised into hills and mountains, of various degrees of height, direction and continuity. On either side of these more elevated regions, the strata dip with more or less inclination, towards the lower spaces between one mountain range and another. (See Pl. 1.)

This disposition in the form of Troughs or Basins, which is common to all formations, has been more particularly demonstrated in the Carboniferous Series, (See Pl. 65. Fig. 1, 2, 3.) because the valuable nature of beds of Coal often causes them to be wrought throughout their whole extent.

One highly beneficial result of the basin-shaped disposition of the Carboniferous strata has been, to bring them all to the surface around the circumference of each Basin, and to render them accessible, by sinking mines in almost every part of their respective areas; (See Pl. 65. Figs. 1, 2, 3.) An uninterrupted inclination in one direction only, would have soon plunged the lower strata to a depth inaccessible to man.