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and " bedding planes " — as geologists call the horizontal dividing 

 lines between the strata — are the results of earth movements and 

 pressures exerted after the rocks had been elevated into dry land. 

 Since then they have been widened and extended by water action, 

 and by frost in severe winters, acting through long ages of 

 geological time. These fissures and joints give us the clue to 

 the formation of the Gorge. 



But before this process began the former sea bottom had 

 become dry land, and the future Mendips had appeared for the 

 first time out of the waters. This new land surface was at once 

 attacked by forces, which set to work to alter and modify 

 it. These were the forces of sub-aerial denudation," or the 

 denudation or eating away of land exposed to the atmosphere, 

 by water — whether as rain, or streams or ice — by wind and by 

 chemical action. When the first rains poured in torrents upon 

 the new land the water began to run off the higher grounds to 

 the lower, and ultimately to the sea. But, owing to the peculiarity 

 of the limestone surface, a curious thing happened, for instead 

 of the water flowing regularly downwards as ordinary streams 

 do, these streams only got so far as the nearest fissure or crevice 

 in the limestone, and, plunging down this, between the joints, 

 disappeared from the surface. And this occurred all over the 

 new land area, the water everywhere tended to leave the surface 

 and continue its course underground. This sudden vanishing of 

 surface waters, streams, and even rivers, into cracks and fissures 

 is a feature common to the drainage of limestone districts. It 

 is going on to-day as it did countless ages ago, before the 

 Cheddar Gorge was formed. A walk over the Mendips will show 

 numbers of these holes, some with water in them, and many now 

 old and dry. These are known as " swallets," or " swallow- 

 holes," and there are hundreds of them, some large and many 

 small, all over the high Mendip plateau. Now, it is to this 

 curious behaviour of water, which is peculiar to limestone districts, 

 that the formation of Cheddar Gorge is due. 



To understand this we must trace the process further, and 

 consider what happens after a stream has disappeared into a 

 fissure between the limestone blocks. Where these joints are well 

 shown it can be seen that their bases are formed by a line of 

 bedding or stratification, and the same earth movements that split 

 the joints have loosened these, so that a line of weakness is formed 

 between the two layers of stone. Along this the water soon makes 

 its way in a more or less horizontal direction, until it meets another 

 vertical fissure separating two other joints further down. Into 

 this it will flow, and then again along another bedding plane to 

 a fissure further beyond. In this manner, by a succession of long 

 steps, water finds its way through crevices in the massive rock, 

 until it issues into the light of day, at the base of the limestone 

 cliffs. The re-appearance of such streams can be seen in many 

 places along the bases of the Mendips. We have examples in 



