198 



THE WONDERS OF GEOLOGY. 



Lect. HI.- 



The oolitic system of Yorkshire affords examples of these 

 alternations of marine and fluvio-marine strata. 



5. Displaced strata. — But though the sedimentary 

 strata have originally been deposited in horizontal layers, 

 yet this arrangement has subsequently been disturbed by 

 expansive internal forces, which have occasioned the ele- 

 vation of some areas and the depression of others, by which 

 the strata have been broken up, and thrown into every 

 direction, from a slight degree of inclination, to a vertical 

 position. 



It will therefore be requisite in this place to explain 

 a few scientific terms which are frequently employed to 

 express these phenomena ; for though it is my wish to 

 abstain as much as possible from technical language, it 

 cannot in all cases be avoided without incurring incon- 

 venient circumlocution. Parallel layers or strata, placed 

 horizontally upon each other, as a, &, c, d, in the annexed 



1 'K - I' ' • 



Lign. 32.— Illustrative of Stratification. 

 a, b, c, d, Horizontal strata in a conformable position, resting unconformably on 



the inclined strata, 1, 2, 3, 4. 

 1, 2, 3, 4, Strata in an inclined position, and severed and displaced by a fault,/. ' 



diagram (Lign. 32), are said to be conformable ; but when 

 strata are superimposed on others which lie in a different 



