FIG. 8. PART OF HARRISBURG QUADRANGLE. PA.	SCALE.	1:82,300;	CONTOUR INTERVAL, 20 FEET
Like the rest of us, Pennsylvanians are proud of the State they live in, and with good right; yet how few of them know their home geography I How few of them can give any adequate account of the “ water-gaps ” by which the Susquehanna makes its way through the long, even-crested ridges that run athwart its course, or of the long, narrow valleys between the close-set ridges. How few know that where the main line of the Pennsylvania railroad crosses the river above Harrisburg, the piers of the
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FIG. 9. PART OF HOLLIDAYS BURG QUADRANGLE. PA. SCALE. 1: 62,500; CONTOUR INTERVAL, 20 FEET
bridge rest on the worn-down reefs of the same hard sandstone that rise on either side in one of the mountain ridges! When you next meet a Pennsylvanian ask him to describe the curious zigzag pattern by which so many of his Alleghany ridges shift their course, and see if he can give an account that would not be much bettered by studying the above map of Loop mountain. Ask him again how the ridges have been formed, and see if he can give the simple answer that they are the harder beds of tilted sandstones, left in relief because the weaker adjoining beds of shales and limestones are weathered down to a lower level, just as the harder grain of a weathered board is left in relief after the softer parts are worn out. There are of course some persons who are so engrossed in other things that they do not care to know about ridges and valleys, but fortunately there are many other persons to whom outdoor nature is absorbingly interesting. For them, a walk southward, map in hand, up the open valley of Oldtown run to its narrowing head, a scramble westward up the forest-clad mountain-side to the triangulation station at an altitude of 2,470 feet, and a descent down the benched slope to Plum creek valley, would make a holiday worth having.
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