The pictorial sketch-book of Pennsylvania : or, its scenery, internal improvements, resources, and agriculture, popularly described . % fig. 37. lying in an unconformable position to the more modern overlayingsurface. Various -writers have cautioned the observer against certain decep-tive appearances of the strata in particular lines of coast, (which areno less frequent in our mountain regions,) where beds, apparentlyhorizontal, in reality dip at a very considerable angle. The follow-ing fig. 38, exhibits a headland as seen from the south, in whichthe strata appear to the eye perfectly level.


The pictorial sketch-book of Pennsylvania : or, its scenery, internal improvements, resources, and agriculture, popularly described . % fig. 37. lying in an unconformable position to the more modern overlayingsurface. Various -writers have cautioned the observer against certain decep-tive appearances of the strata in particular lines of coast, (which areno less frequent in our mountain regions,) where beds, apparentlyhorizontal, in reality dip at a very considerable angle. The follow-ing fig. 38, exhibits a headland as seen from the south, in whichthe strata appear to the eye perfectly level. There appears to be nomistake about their horizontal position; but if the headland treads. fig. 3S. off, at the point p, in fig. 39, to the northward, affording a view ofthe cliffs westward, it will be seen that the appearance from thesouth is defective, for the lines here show a considerable angle to thenorth, and gradually increasing in their dip, finally become verticalat a. It has already been intimated that fossiliferous rocks follow aninvariable order of succession, but that the arrangement, althoughnever reversed, is sometimes imperfect; so that, while we never meetb going before a, or c preceding b, yet we occasionally miss not onlya single letter, but a succession of letters, and find, in certain locali- ANTHRACITE COAL FORMATION 151


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Keywords: ., bookcentury1800, bookdecade, booksubjectminesandmineralresources