needham] the lay of the land 15 



from the solid rock, gravity disposes of them : removes them 

 almost as fast as formed from the vertical face of the cliff: 

 lets them lie on the level summit: sweeps them down the 

 slope: spreads them out over the flood plain, making level 

 fields; or carries them far away with the rushing flood to 

 dump them into the bottom of the sea, where, removed from 

 light and air, they are lost to our use. 



Thus the rugged and geologically ancient outlines of 

 topography are softened by erosion and overspread by a 

 mantle of productive soil. Erosion rounds off the sharp 

 edges of the headlands; silting fills the low places; delta 

 building covers the shores about the mouths of streams; 

 everywhere as time runs on, sinuous lines replace the sharp 

 angles, and verdure replaces the gray pristine desolation 



Let us go to some good point of outlook, some hill-top or 

 housetop or tower, and view the topography of our own 

 neighborhood, to see how the land lies. We will let our eyes 

 wander slowly from the near-by fields upward to, the summit 

 of the distant hills, and downward to the level of the valley; 

 we will follow the stream that meanders across the valley 

 floor, back to its more turbulent tributaries, and on to the 

 little brooks that run among the hills. Upland and lowland 

 levels, and intervening slopes: — these are the natural divi- 

 sions of the land ; and their boundaries are all laid down by 

 gravity. Water runs down hill, and loosened soil materials 

 move ever with it. They may glide unnoticed as tiny films 

 of sediment trickling between the clods of the fields ; or they 

 may move in great masses of earth and stone as a landslide, 

 scarring the face of the steep slope ; but ever, with the aid of 

 water, they move to lower levels, and slowly the form of the 

 hill is changed. Flood plains broaden: valleys are filled; 

 the slope grows gentler ; and the upland plains are narrowed 

 by invading rills. 



Outspread before us as we look abroad over the landscape, 

 with its levels of checkered fields, its patched and pie-bald 

 hills, its willow-bordered streams and reedy swales, is this 

 blanket of soil, which seems so permanent, yet which is 

 forever shifting to lower levels. 



Water, descending, follows the lines of least resistance. 

 Hence, from every high point, slopes fall away in all dircc- 



