. Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments. Geology. Oh. V.] DIP AND STKIKE. 55 line, it will be seen that the amount of inclination may still be measured by the hands with equal facility. It has been already seen, in describing the curved strata on the east coast of Scotland, in Forfarshire and Berwickshire, that a series of con- cave and convex bendings are occasionally repeated several times. These usually form part of a series of parallel waves of strata, which are pro- longed in the same direction throughout a con
. Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments. Geology. Oh. V.] DIP AND STKIKE. 55 line, it will be seen that the amount of inclination may still be measured by the hands with equal facility. It has been already seen, in describing the curved strata on the east coast of Scotland, in Forfarshire and Berwickshire, that a series of con- cave and convex bendings are occasionally repeated several times. These usually form part of a series of parallel waves of strata, which are pro- longed in the same direction throughout a considerable extent of country. Thus, for example, in the Swiss Jura, that lofty chain of mountains has been proved to consist of many parallel ridges, with intervening longi- tudinal valleys, as in fig. 71, the ridges being formed by curved fossilif- erous strata, of which the nature and dip are occasionally displayed in deep transverse gorges, called " cluses," caused by fractures at right angles to the direction of the chain.* Now let us suppose these ridges and parallel valleys to run north and south, we should then say that the strike of the beds is north and south, and the dip east and west. Lines drawn along the summits of the ridges, A, B, would be anticlinal lines, and one following the bottom of the adjoining valleys a synclinal line. Fig. Section illustrating the structure of the Swiss Jura. It will be observed that some of these ridges, A, B, are unbroken on the summit, whereas one of them, C, has been fractured along the line of strike, and a portio 1 of it carried away by denudation, so that the ridges of the beds in the formations a, &, c, come out to the day, or, as the miners say, crop out, on the sides of a valley. The ground plan of § such a denuded ridge as C, as given 1 in a geological map, may be ex- ( | pressed by the diagram fig. 72, and | the cross section of the same by | fig. 73. The line D E, fig. 72, is the anticlinal line, on each
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectgeology, bookyear1868
