104 THE FAIRY-LAND Of SCIENCE. 
but these are only rare effects of water. It is when the 
rain collects in brooks and forms rivers that it is most 
busy in sculpturing the land. Look out some day 
into the road or the garden where the ground slopes a 
little, and watch what happens during a shower of 
rain. First the rain-drops run together in every little 
hollow of the ground, then the water begins to flow 
along any ruts or channels it can find, lying here and 
there in pools, but always making its way gradually 
down the slope. Meanwhile from other parts of the 
ground little rills are coming, and these all meet in 
some larger ruts where the ground is lowest, making 
one great stream, which at last empties itself into the 
gutter or an area, or finds its w?y down some grating. 
Now just this, which we can watch whenever a 
heavy shower of rain comes down on the road, happens 
also all over the world. Up in the mountains, where 
there is always a great deal of rain, little rills gather 
and fall over the mountain sides, meeting in some 
stream below. Then, as this stream flows on, it is fed 
by many runnels of water, which come from all parts 
of the country, trickling along ruts, and flowing in 
small brooks and rivulets down the gentle slope of the 
land till they reach the big stream, which at last is 
important enough to be called a river. Sometimes 
this river comes to a large hollow in the land and 
there the water gathers and forms a lake ; but still at 
the lower end of this lake out it comes again, forming 
a new river, and growing and growing by receiving 
fresh streams until at last it reaches the sea. 
The River Thames, which you all know, and whose 
course you will find clearly described in Mr. Huxley's 
