52 53 54 55 56
[Fig. 50] illustrates the basin of a young river or brook, with its slopes and system of drainage, just such an one as may be seen near many country school-houses, and an exaggerated type, only, of what may be found in the streets and alleys of the city. Its source (a) is found in a slight depression which, in the spring or after heavy rains, becomes a pond, from which its waters overflow and trickle down through two channels, which they have worn for themselves. The soil brought down by these rivulets and others which are tributaries to the main stream, may be seen deposited at b, c, d, e, as flood plains, islands, and delta. Notice the cañon cut by one of the tributaries through the left slope of the basin, and the cascade and waterfall where the debris brought down at high water has formed an obstruction. In [Fig. 51] is given a typical Switzerland river basin. [Figs. 52 to 55] inclusive, show ocean wearing and rock weathering. “Hilt Rock” ([Fig. 52]) shows alternate layers of trap rock and sandstone. In [Fig. 53] (“Point Portal,” Pictured Rocks, Lake Superior), is seen the effect of wave and wind wearing in soft rock, and [Fig. 54] (“Land’s End,” Cornwall, England), is an example of wave wearing in hard rock. [Fig. 55] (“Giant’s Cause-way,” Ireland), shows the weathering and wearing of basaltic rock. [Fig. 56] is Eddystone Light-house, (England).
57 58 59 60
In the drawing of maps, the meeting of land and water can be as accurately drawn by the new method as by the old. The following sketches illustrate the fact that it is not necessary to use any line running contrary to the general direction of surface, in order to represent any contour of coast.
[Figs. 57 to 60] are imaginary bird’s-eye views of coasts. [Fig. 57] shows a stretch of level land at the coast, with broken or hilly land between it and the distant higher hills or mountains: the latter being merely suggested in the representation. A stream winds its way through the low land to the ocean, where the silt which it has brought down and the sands which have been washed up by the sea, form a delta and sand-bars. [Fig. 60] shows drowned valleys, fiord coasts, and continental islands.