ON CAVES. 61 



than six inches in thickness ? The coal would thus 

 be protected from further abrasion, and the further 

 demolition of the cliff prevented. 



94. A mural cliff consisting of basalt, called the 

 King's Craig, is situated between the towns of 

 Burntisland and Kinghorn, and is considerably ele- 

 vated above the present level of the sea. At the 

 bottom of the craig, a thin stratum of coal, about 

 an inch in thickness, extends the whole length of 

 the base. Now, whence came the perpendicularity 

 of that rock ? and whence its mural aspect ? Was 

 that rock, at a former but remote period, exposed to 

 the action of the waves ? and because of this, the 

 stratum of coal at the base of the cliff would 

 undergo a much more rapid abrasion than the rock 

 above ; and, therefore, the exposed part of the 

 superincumbent rock would, from time to time, be 

 left unsupported, which, giving way, a mural cliff 

 presenting a perpendicular face would be formed ? 



ON CAVES. 



95. What is the origin of those caves which 

 occur in the cliffs upon the sea-shore, and which 

 present somewhat the form of a hollow sphere ? 

 Are they formed thus In a cave which presents 



