Dr. Ricketts — On Fissures, Faults, Contortions, etc. 207 



result from depression or from upheaval, is larger than it was 

 originally, upon a change to upheaval or depression, as the case 

 may be, the strata must be compressed into a smaller compass, and 

 therefore foldings and contortions will be induced, the general 

 direction lengthwise being the same as that of the faults. This 

 same action would originate cleavage; but not in any beds which 

 have been elevated above the sea-level, as, in consequence of the 

 drainage of the water they contain, such consolidation would take 

 place that the necessary movements amongst their constituent 

 particles would be rendered impossible. 



This method of accounting for the production of contortions was 

 first proposed by Prof. Phillips in 1848,^ and was afterwards, but 

 independently, used by the late Prof. Jukes, to account for the 

 formation of certain contortions observed by him in the Coal-strata 

 of Staffordshire.* 



In this and in a previous communication (Geol. Mag., Vol. IX., 

 p. 119) my endeavour has been to prove the strict interdependence 

 of geological phenomena. Change cannot take place in one direction 

 without causing alteration in another. Prolonged and almost im- 

 perceptible are the actions that have produced the immense amount 

 of denudation on the earth's surface ; fully as slow has been the re- 

 deposit in other localities of the debris resulting from that denuda- 

 tion. The most enormous contortions, and the most abrupt bendings 

 of strata, as well as that change in the position of the constituent 

 particles by which slaty cleavage has been induced, have occurred 

 in the most gradual manner. They have been effected with great 

 power, it is true, but without violence. I believe the time must 

 shortly arrive when it will be generally accepted by geologists that 

 " the most gigantic curvatures of strata have been the result of intense 

 pressure so moderated in its application as to have been just sufficient 

 to overcome the resistance opposed to it, and that this motion has 

 been as insensible as the unfolding of the petals of a flower."^ Even 

 the volcano and the earthquake must be removed from the category 

 of cataclysms and convulsions. With more probability may they be 

 considered as the necessary result of those slow and imperceptible 

 changes, by whose accumulated power certain physical alterations 

 have been made in the earth's crust. In conclusion, I must express 

 my conviction that a careful examination of the phenomena under 

 consideration will demonstrate that the prime mover which has 

 produced them is denudation, with its consequent deposition, acting 

 and re-acting on the crust of the earth, equally balanced on its fluid 

 interior. 



1 Memoirs of the Geological Survey, vol. ii. Geology of the Malvern Hills, p. 142. 



2 Student's Manual of Geology, chap. xiii. 



^ Sir C. Lyell, Presidential Address, 1850, Quart. .Tour. Geol. Soc, vol. vi., p. Ixiii. 



