THE MOOR, OR UPLAND. 303 



which would spoil vegetation if it fell wholly upon the 

 cultivated plains, and cause overwhelming floods, if it 

 fell upon the narrow tops, or steep sides of mountains. 

 Thus, though a moor be the least like a lake of any 

 of the broad features of a country, it serves some of 

 the most important purposes of one. Moors are very 

 generally composed of beds of gravel, far more gene- 

 rally than of any thing else. They are the waste of 

 mountains collected together by causes which we 

 cannot explain. This gravel is porous to a great 

 depth in some places, and to a smaller depth in others ; 

 and there are some in which it is made retentive by clay, 

 or rendered so by the accumulation of moss. Thus 

 it answers as a set of reservoirs, placed at various 

 elevations, from which springs are given out all along 

 the slopes that descend from it; and those clear 

 fountains and crystal streams, which add so much to the 

 beauty and fertility of the little sheltered glens and 

 dells with which the slopes from an elevated moor 

 abound, owe their existence to the apparent sterility 

 of its surface. The heath, with the mosses and lichens 

 with which the spaces between the roots of the heath 

 are usually filled, prevent the water from running off 

 the surface, even where the obliquity is considerable ; 

 and while the mosses and lichens retain as much of it 

 near the surface as suffices for the nourishment of them- 

 selves and the heaths, the roots of the latter penetrate 

 farther into the ground, and serve as conducting pipes 

 to the more porous strata. The heath also shades, 

 from the action of the sun and atmosphere, those more 

 lowly plants which arrest a portion of the humidity 

 in its motion downward ; and thus there is little waste 



