107 



In other cases, one series of strata meets ano- 

 ther at some angle; and this occurrence hap- 

 pens most frequently where the primary are fol- 

 lowed by the secondary strata, but is by no means 

 confined to these. In such a contact, the planes 

 of the superior strata may lie on the edges of the 

 inferior ; a position known by the terms uncon- 

 formable and overlying. Otherwise, the edges of 

 the superior may abut against the planes of the 

 inferior. There are cases moreover, in which one 

 stratum, or series of strata, may be both parallel 

 and unconformable to the series immediately be- 

 low it ; being in contact with the edges in one 

 place and with the planes in another. 



In a succession of strata, the angle of inclina- 

 tion is sometimes found gradually to increase, or 

 to diminish, according to the mode in which they 

 are examined. In this way, strata pass gradually 

 in some cases, even from the horizontal to the 

 vertical position. 



Some cases occur in which this disposition 

 takes place in a corresponding manner on both 

 sides of a vertical stratum, or set of vertical strata. 

 In such instances, the strata have been said to ra- 



