. Elements of geology. Geology. 68 LYELL'S ELEMENTS OF GEOLOGY. Origin of Curved Strata Zigzag Flexures. other books to each end, and force them towards each other. The folding of the cloths will exactly imitate those of the bent strata. (See Fig. 61.) To inquire whe- ther the analogous flexures in strata have really been due to similar side- way movements, or other exertions of force, would lead me farther into the regions of specula- tion and conjecture than might be consistent with the scope of this elementary work. When the volcanic and granitic rocks are described, it will be seen that so
. Elements of geology. Geology. 68 LYELL'S ELEMENTS OF GEOLOGY. Origin of Curved Strata Zigzag Flexures. other books to each end, and force them towards each other. The folding of the cloths will exactly imitate those of the bent strata. (See Fig. 61.) To inquire whe- ther the analogous flexures in strata have really been due to similar side- way movements, or other exertions of force, would lead me farther into the regions of specula- tion and conjecture than might be consistent with the scope of this elementary work. When the volcanic and granitic rocks are described, it will be seen that some of them have, when melted, been in- jected forcibly into fissures, while others, already in a solid state, have been protruded upwards through the incumbent crust of the earth, by which a great displacement of flexible strata must have been caused. It also appears that cavities are sometimes formed in the interior of the earth, whether by the removal of matter by volcanic action, or by the contraction of argillaceous rocks, or other causes. In this manner pliable beds sinking down, from failure of support, into chasms of less hori- zontal extent, may have become folded and compressed laterally. Such subsidences have been witnessed on a small scale in the undermined ground immediately over coal-pits, from which large quantities of coal and stone had been extracted. Fig. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Lyell, Charles, Sir, 1797-1875; Gibbes, Lewis Reeve, 1810-1894, former owner. DSI; Merrill, George P. (George Perkins), 1854-1929, former owner. DSI. Philadelphia : James Kay, Jun. and Brother ; Pittsburgh : C. H. Kay & Co.
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