THE HISTORY OF THE GROUND. 2/ 



away whole mountain ranges in a very short time. In 

 the West we find that this work of carrying away the 

 ruins of degraded hills is going on now upon the most 

 gigantic scale, and from this we can form an idea of 

 what may have happened long ago. Currents and 

 tides along the shore are also movers of sand and 

 gravel, moving beaches and sand-bars from place to 

 place, and often changing the whole character of the 

 coast for miles. 



We observed, in studying the empty bed of the riv- 

 ulet, that the sand after the water had subsided is left 

 in one place, the fine mud in another. This is often 

 shown on a small scale in every street-gutter ; and, to 

 the young man or young woman with eyes, the street 

 may be an open lesson in the first principles of geol- 

 ogy. Running water is thus the great rock-sorter, as 

 well as rock-mover. The ruins of the hills are not left 

 in hopeless confusion on the plains. The whole of the 

 material is completely sorted : the larger stones and 

 pebbles are left in one place ; the sand is carried 

 farther away, and is left by itself ; and the lighter stuff, 

 the mere specks and scales of rock, are carried farthest, 

 and left also by themselves. We saw in our studies 

 of the weather, that the sun brought the water from 

 the seas, and that the invisible vapor in the air con- 

 densed as clouds about the cold mountain-tops, to fall 

 in rain. We now see that this same rain assists to 

 break down the rocky hills, and to carry the ruins far 

 and wide, and leave the sand and fine silt or mud on 

 the lowlands to cover the naked rocks, and form a 



