486 GEOLOGICAL REVOLUTIONS. CHAP. 



probable is the following: Conceive the rising- of land in the 

 direction described to have been gradual, and angular, so that 

 first the parts about D H, next those about C G, and finally those 

 about BE, appeared above the water. The effect would be some 

 degree of waste on every part by the action of the troubled sea 

 along every freshly presented line of coast ; the softer parts would 

 be wasted in a higher degree, and through greater depths of water, 

 so as to form the hollows in question. Irregularities would arise, 

 projections as at p, recessions as at r, outliers as at o. The firm 

 rocks might have continuous plane surfaces of considerable extent, 

 so that a given bed of stone, of no great thickness, e. g. cornbrash, 

 might occupy the ground for a mile or more in breadth, and for 

 ten or twenty or more miles in length, without a particle of Oxford 

 clay resting upon it ; though in other places outliers of this clay 

 might appear in small patches dotted on the stony slope. 



There can be no doubt about the truth of this reasoning ; but 

 something further is to be stated. The rising of the land above 

 the mean level of the sea is a measure of great mechanical energy : 

 under such an effort the rocks are strained ; they yield unequally 

 among themselves, unequally and in various directions at different 

 localities in the area subject to elevation. 



Diagram OCX. Waste of the Earth's Surface. 



I. Let A, J5, (7, D be a tract of stratified rocks, (ti) hard, (s) soft, 

 elevated above the sea-level A, D, E. In this tract, in consequence 

 of the movement of elevation, let there be lines of weakness arising 

 from partial discontinuity of the masses (whether produced by faults 

 or not), as represented by dots. 



3. Let the movement be supposed at an end, the country settled, 

 rain falling. The rain will enter the ground more freely on the 

 lines of weakness. It will flow in the direction of these lines 



