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the subterranean stream which comes out into the light of day 

 opposite the Lion Rock, at the opening of the Gorge at Cheddar. 

 Similarly, the River Axe issues from the well-known cave at 

 Wookey, near Wells. 



So must have occurred the first step in the making of the 

 Gorge. The stream which commenced this great work of Nature 

 began to flow very soon after the upheaval of the Mendips from 

 the old coral sea. It soon made its way through fissures, as has 

 been explained, in the course of what is now the gorge. And 

 now, having established its channel, in the direction which was 

 some day to become so famous, it set to work to widen and enlarge 

 this by a method, for the understanding of which a little know- 

 ledge of chemistry is requisite. Most of us know that the atmos- 

 phere contains a trace of a gas known as Carbonic Acid. This 

 gas is soluble in water, and hence is absorbed by rain as it falls. 

 Now, water containing Carbonic Acid Gas will slowly dissolve the 

 lime (or carbonate of lime, as it is called) out of limestone, and 

 carry it off in solution. The streams then, in flowing through the 

 fissures and crevices of the limestone, gradually dissolve the 

 stone, much as a lump of sugar dissolves in tea, only very much 

 more slowly. This causes a continuous enlargement and widening 

 the fissures, which, in the course of ages, cause huge masses 

 of rock to become loosened by the water dissolving the 

 surfaces and edges over which it passes. Thus cavities are 

 formed, which gradually enlarge into long caverns, always con- 

 nected by spaces and fissures through which water flows from one 

 to another in its downward course. Loosened rock masses tend 

 to fall down and partially block up these spaces ; but the water 

 at once begins its work of dissolving, loosening, and washing out 

 fragments, and finding its way into fresh crevices, continually 

 weakens and eats away the rock in its subterranean passage. 

 Hence it follows that such limestone hills as the Mendips, in the 

 course of ages, have become honeycombed with underground 

 caves, channels and water passages. Some are now dry, having 

 been deserted by the streams which formed them, which are now 

 flowing at a lower level ; others are full of swiftly moving water. 

 Recently some of these have been explored by intrepid investi- 

 gators, and the course of certain underground streams mapped 

 out in the Mendips, and especially in Yorkshire, where a Society 

 of cave-explorers has been at work for some years. But while 

 this cavern-forming process has been going on for ages under- 

 ground, the ordinary processes of wind and weather have been 

 slowly dissolving the limestone from above by surface denudation. 

 Hence it sometimes happens that the roof of one of these caverns 

 becomes very much thinned partly from above, and also by 

 dripping water dissolving it from below. So, presently it cracks, 

 the roof gives way, and a portion falls, disclosing the cave and 

 water passages beneath it. Such an opening, once made, »s 

 rapidly enlarged. The cave walls and roof speedily break away 



