MR CADELL ON EXPERIMENTAL RESEARCHES IN MOUNTAIN BUILDING. 355 



On the suggestion of my colleague Mr B. N. Peach, who helped to carry out this last 

 series of experiments, the upper folded clay bed was stripped off, and the surface of the 

 lower bed laid bare. It was found covered with a series of minute sharp corrugations 

 transverse to the direction of movement and parallel to the main ridges- above (fig. 24). 



Fig. 25. 



A similar experiment was made with somewhat thicker strata, but instead of all the 

 beds being plastic, the upper layers were of brittle materials like those used in the first 

 and second series of experiments. On permitting contraction to take place, the upper 

 brittle beds broke into cakes, which were at places thrust over one another for short 

 distances (tig. 25). 



Fig. 26. 



On removing the upper strata, the tenacious bed adhering to the caoutchouc was found 

 as before covered with minute corrugations (fig. 26). 



On stretching the band slightly, the corrugations were not flattened out, but the clay 

 split along a series of vertical cracks, parallel to the minute puckerings on its surface. 

 The sides of these little fissures were observed to be covered with minute vertical striations. 

 and had the appearance of slicken-sided faults, along which vertical movement had taken 



