EXPERIMENTS 



257 



ential motion of the layers, each bed rising farther up the slope 

 than the one beneath it. The same thing must occur in folded 



FIG. hi. — Model showing the slip of folded beds upon one another. (Willis.) 



rocks, which sometimes show polished bedding planes, due to the 

 slipping of the beds upon one another. The series A to D (in 

 Fig. 112) represents a model before and in various stages of 

 lateral compression, 

 and exhibits the 

 effect of the slight 

 initial dip at x in 

 determining the po- 

 sition of the anti- 

 clinal fold, which is 

 developed by com- 

 pression. The for- 

 mation of one fold 

 assists in the devel- 

 opment of another, 

 for it both changes 

 the direction of the 

 thrust and redistri- 

 butes the load of 

 overlying strata. 

 The arch of the an- 

 ticline lifts the load 

 and diminishes the 

 s 



FIG. 112. — Model showing effects of lateral compres- 

 sion. A, before folding, with slight initial dip at x ; B, 

 C, D, in various stages of compression. (Willis.) 



