103 



contortion ; and, in such cases, the fractured ends 

 sometimes remain in contact ; at others, they are 

 shifted so as no longer to be in the same plane ; 

 and, at others again, are separated by veins of in- 

 tervening materials. 



In one rock only, it has been observed that a 

 stratum will in one part lose its character and be- 

 come a shapeless mass. This happens where se- 

 condary limestone is in contact with the primary 

 rocks ; and also where it is in the vicinity of trap. 

 The Isle of Man, and Sky, furnish examples of 

 l>oth these facts. 



The positions of strata vary from the horizon- 

 tal to the vertical, through every intermediate 

 angle. 



The horizontal position requires no further 

 remarks ; but the inclination of the others to the 

 horizon is called the dip ; in which term is fur- 

 ther implied its tendency towards some point of 

 the compass, where it is not vertical ; while the 

 quantity of that inclination is expressed in the 

 number of degrees by which it deviates from the 

 horizontal position. 



If a vertical stratum be assumed, of which the 



