. Elements of geology : a text-book for colleges and for the general reader. Geology. Fig. Fig. row gorge out on an open plain. The lateral spreading of the glacier causes it to crack longitudinally (Fig. 59). Fig. 60 is a longitudinal vertical section of the same. Veined Structure.—Tyndall has shown conclusively that veins are always at right angles to the line of greatest pressure, and that, there- fore, they are produced by press- ure. Thus fissures and. veins, being produced by opposite causes—one by tension and the other by pressure—are formed under opposite conditions. As transverse
. Elements of geology : a text-book for colleges and for the general reader. Geology. Fig. Fig. row gorge out on an open plain. The lateral spreading of the glacier causes it to crack longitudinally (Fig. 59). Fig. 60 is a longitudinal vertical section of the same. Veined Structure.—Tyndall has shown conclusively that veins are always at right angles to the line of greatest pressure, and that, there- fore, they are produced by press- ure. Thus fissures and. veins, being produced by opposite causes—one by tension and the other by pressure—are formed under opposite conditions. As transverse fissures are produced by the longitudinal stretching of a glacier passing over a sa- lient angle, so transverse veins Fig. 60. are formed by the longitudinal compression of a glacier passing over a re-entering angle. Fig. 60 is a section of the Ehone glacier (Fig. 59), showing the crevasses (c c c) produced by the steep declivity, and the veined structure (s s s) produced by the compression conse- quent upon the change of angle on coming out on the plain. The relation of crevasses and vein-structure is still bet- ter shown in the ideal sec- tion (Fig. 61). Again, as marginal fis- sures are produced by the pulling of the central por- tions upon the lagging margins behind, so the marginal veins are produced by the crowding or pushing of the swifter central parts on the slower marginal parts in front (Fig. 62). The marginal veins are, therefore, inclined to the margin about 45°, but. 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 LeConte, Joseph, 1823-1901. New York : D. Appleton and Co.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectgeology, bookyear1892
