MOUNTAIN FORMATION 



There may be local tremors due to causes which are less 

 immense and world-wide. One such cause might be the 

 collapse of cavities in the earth. We are well acquainted 

 with some such caves near the surface of the earth. These 

 caves, especially in limestone, are commonly caused by the 

 action of springs. Even pure water will dissolve a minute 

 quantity of the substance of many rocks, and rain water 

 is far from being chemically pure water. It takes oxygen 

 and carbonic acid out of the air as it falls, and it abstracts 

 acids out of the soil through which it sinks. The pre- 

 sence of this acid gives the water a greatly increased 

 power of attacking carbonate of lime. Now limestone is 

 a rock almost entirely composed of carbonate of lime. It 

 occurs in most parts of the world, covering sometimes 

 tracts of hundreds or thousands of square miles, and 

 often rising into groups of hills and ranges of mountains. 

 The abundance of this rock offers ample opportunity for 

 the display of the dissolving action of subterranean 

 water. The water trickles down the vertical fissures along 

 the planes below the limestone beds. As it flows on it 

 dissolves and removes the stone till in the course of cen- 

 turies these passages are gradually enlarged into clefts, 

 tunnels, and caverns. The ground becomes honeycombed 

 with dark subterranean chambers, and running streams 

 fall into these chambers and continue their course under- 

 ground. 



In England there are famous "pot-hole" caverns in York- 

 shire and the west of England. The Peak Cavern in 

 Derbyshire is believed to be 1200 feet long, and in some 

 places 120 feet high. The caverns of Adelsberg near 



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