356 MR CADELL ON EXPERIMENTAL RESEARCHES IN MOUNTAIN BUILDING. 



place. In this case the horizontal pressure being uniformly exerted from particle to 

 particle along the band, and not at one point as in former experiments, had produced a 



Fig. 27. 



general " staving together " throughout the mass, causing the particles to move upwards 

 along vertical planes transverse to the line of greatest pressure (fig. 27). 



In this experiment we have a possible explanation of the origin of great areas of 

 vertically cleaved rock known to exist at the roots of old mountain systems. The bed 

 below has undergone what appears to be cleavage, while that at the surface has been 

 thrown into folds without any considerable interstitial movement. 



If the folded surface of the clay be taken to represent the waxcloth in series B, the 

 theory of a uniformly contracting sole might explain not only regional metamorphisro , 

 but the phenomena of fan structure, thrusting, and wedge structure as well. 



D. General Summary of Results. 



1. Horizontal pressure applied at one point is not propagated far forward into a mass 

 of strata. 



2. The compressed mass tends to find relief along a series of gently-inclined " thrust - 

 planes," which dip towards the side from which pressure is exerted. 



3. After a certain amount of heaping up along a series of minor thrust-planes, tin 

 heaped-up mass tends to rise and ride forward bodily along major thrust-planes. 



4. Thrust-planes and reversed faults are not necessarily developed from split overfolds. 

 but often originate at once on application of horizontal pressure. 



5. A thrust-plane below may pass into an anticline above, and never reach the surface. 



6. A major thrust-plane above may, and probably always does, originate in a fold 

 below. 



7. A thrust-plane may branch into smaller thrust-planes, or pass into an overfold along 

 the strike. 



8. The front portion of a mass of rock being pushed along a thrust-plane tends to bow 

 forward and roll under the back portion. 



