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manner dependent upon the character of the surface. After a dry 
season peat, for example, takes up rain water almost as greedily as 
a sponge would do; and for a very long time after the wet season 
commences, nearly every drop of rain that falls on a peat moss, 
dry to begin with, soaks into the peat and for a time stays there. 
After a while the peat becomes saturated, water oozes out of the 
sides of the hags—if we are dealing with fell-peat—and thence is 
delivered slowly and steadily into the head waters of the streams, 
and so on down to the sea. Loose sand, shingle, and many other 
rocks of the same kind, behave in like manner; they, too, soak up 
the water as fast as it reaches them, and allow it to percolate 
downward to the point where a change of porosity sets in. Lime- 
stone, again, where not capped by clay or other watertight 
material, allows the water to sink into its joints to almost any 
extent. In the wonderful expanses of perfectly bare grey lime- 
stone, such as Orton Scar and similar areas south of Appleby, rain 
may fall in torrents and yet not a pint of it will flow more than a 
dozen yards or so over the limestone. As well might one try to 
fill a sieve with water as to get up a small stream on limestone 
areas cut up by rock-fissures innumerable as these are. As fast as 
the rain falls on a surface of that kind, down it goes, and is, 
apparently, lost to sight for ever. 
Orton Scar is, it is true, something out of the common, but it 
serves well to illustrate an extreme case. As another extreme we 
might take some of the areas of Silurian rocks, such as those of 
‘the Howgill Fells, where the rocks are more or less impermeable, 
and where a very large proportion of the rainfall is swept at once 
into the becks, and only a small percentage sinks in. If we 
compare the surface features of the two areas (which adjoin) we 
shall find no streams at all (or practically none) on Orton Scar, 
while on the opposite or south bank of the Lune, watercourses 
abound. Yet the rainfall is nearly the same over both areas; only in 
the one the water flows off almost as fast as it comes down, while in 
the other it sinks inte the rock and disappears underground. It 
is the same everywhere, hence the permeability or impermeability 
of the surface rocks is a matter of considerable importance in 
