. Off-hand sketches : a companion for the tourist and traveller over the Philadelphia, Pottsville, and Reading railroad . aving been forced through the superincumbent rocks, hasborne them upwards in its ascent; the strata in the vicinity of themountain, «, being raised at an acute angle at b, and sinking to 148 OFF-HAND SKETCHES nearly a level position in the plains at c. The form and successionof these rocks, says Prof. Richardson, prevail all over the earth, withsome local exceptions: so that its entire surf\ice may be consideredto form a series of basins, of which the largest, deepest, and
. Off-hand sketches : a companion for the tourist and traveller over the Philadelphia, Pottsville, and Reading railroad . aving been forced through the superincumbent rocks, hasborne them upwards in its ascent; the strata in the vicinity of themountain, «, being raised at an acute angle at b, and sinking to 148 OFF-HAND SKETCHES nearly a level position in the plains at c. The form and successionof these rocks, says Prof. Richardson, prevail all over the earth, withsome local exceptions: so that its entire surf\ice may be consideredto form a series of basins, of which the largest, deepest, and thickestlie at the bottom., and are filled up by others, which become smaller,shallower and thinner as they approach the top—the deposits beinguplifted and raised towards the edges of these basins, and becomelevel, or nearly so, towards the centre. The inclination of strata from a horizontal position is called theirdip, the amount of the dip being the quantity of the angle which theline of inclination makes with that of the horizon, as in the accom-panying figure, 32. If the angle made by the meeting of the lines. FIG. 32. of the strata, hh, and the horizontal line, a, be equal to forty-fivedegrees towards the east, the strata are said to dip to that extent inthat direction. Again, the terms dip and strike of strata will be fur-ther understood—(for these are terms in universal use in mining,) bythe following illustration: The dip, as before observed, is the linewhich the strata makes with the horizon—the strike being a line atright angles to the dip. To illustrate; place a book on a table, withthe edges of the leaves downwards, and the back of the book up-wards, as in the accompanying figure, 33. Ifone side of the cove? be removed a short dis-tance, the cover so moved, h, will representthe line of dip, while the back of the volume,a, a, will exemplify the line of strike. If thecover of the book be extended only in a slightdegree, the dip, of course, will be proportionall
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Keywords: ., bookcentury1800, bookdecade1850, bookidoffhandsketc, bookyear1854
