392 THE HOME, FARM AND BUSINESS CYCLOPEDIA. 



ACTION OF RUNNING WATER. Particles of sand or clay once detached 

 from the parent rock are quickly carried away by the action of running 

 -water, and as these runnels gain strength and converge into mountain 

 streams and torrents, a new manifestation of the power of water is ex- 

 hibited in the wearing and undermining action which they invariably dis- 

 play. The attention of tourists on the Alps is often called to deep gorges, 

 at the bottom of which is heard the gurgling of the stream. The wearing 

 or cutting action is to be unmistakably traced through the compact rock 

 from the top to the bottom of this gorge, in the water-worn hollows where 

 the stream has evidently eddied and whirled at some remote period, sixty 

 or eighty feet above its present bed. 



ACTION OF RIVERS. Mountain streams converge into rivers, which carry 

 with them the mineral debris of the mountains, and distribute it over the 

 plains beneath. All large rivers flow, during a portion of their course, 

 through fertile alluvial plains ; and further study shows that these plains 

 have been deposited by the river itself, and are in fact composed of the 

 mud brought from the higher grounds to be deposited at a lower level. As 

 rivers widen towards their estuaries, they often deposit still more exten- 

 sive tracts of " alluvium," or mud. 



The Ganges in India, and the Mississippi in North America, both afford 

 remarkable instances of the power exercised by rivers in altering the dis- 

 tribution of sea and land. In the latter case, the mud, vegetable matter, 

 and timber, brought down and deposited at or near the mouth of the river, 

 is rapidly filling up the Gulf of Orleans. It is difficult to draw a distinc- 

 tion between the action of the sea and the action of the river in many 

 of these cases, but both agents act in determining the direction of de- 

 position. 



ACTION OF THE OCEAN. Almost at any part of the coast traces of the 

 perpetual struggle between sea and land may be seen. 



ACTION OF ICE. The expansive force of freezing water as a means of 

 breaking down rocks has been already noticed. Ice and frost also play 

 an important part in the formation of soils upon a large scale. The grind- 

 ing action of glaciers upon the sides of the ravines through which they 

 slowly descend for a glacier is not stationary, but is actually a river of 

 ice results in glacial mud, which, as the ice melts at the lower extremity, 

 is carried down by the stream that perpetually runs from the glacier. These 

 streams are rendered milky or turbid by suspended matter, and it is only 

 when they reach the level land at the base of the mountain that they de- 

 posit their burden in the form of alluvial soil. In many cases it is carried 



