Ill 



p. They are apt in that position to run on for 

 tome distance with tittle deviation of direction, to that 



it crop of one of them mi^ht be marked by a straight 

 bar or ^ 37). The influence of the form of the 



Is more and mure upon the outcrop in pro- 

 portion as the strata approach the horizontal 



of a stratum is the line whi h 

 that stratum makes with the surface of the ground. 

 term "outcrop" i ;okcn of as if it were the 



same as the TV <>rd is applied to 



a lino drawn ; ular to r f <| I' 



is the line made by a stratum with the horizon, and 

 shows the general or average direction of that stratum 

 across the country. On a perfectly level piece of 

 ground strike and outcrop must obvious! . , and 



there must likewise be a complete coincidence among 

 .il strata. The more irregular the surface, and the 

 kss inclined the strata, the further must strike and out- 



p depart from each oil 



&: Vrikt to />// There is a further relation 



to be noted as we proceed, viz. the constant depend- 

 of the direction of strike upon that of dip, and 

 the consequent change as the direction of dip 



varies. The strike is of course a mathematical line 

 cutting the dip at a right angle. If the dip is east or 

 west, the strike must be north and south ; if the < 

 north or south, the strike must be east and west. It 

 must not be supposed, however, that the line of strike is 

 always, or even most commonly, a straight one. It can 

 only be so as long as the direction of dip continues 

 uni hanged. 1 :jarativcly brief experience in the 



