352 MR CADELL ON EXPERIMENTAL RESEARCHES IN MOUNTAIN BUILDING. 



at both sides, the structure would have been quite symmetrical. In another experiment a 

 perfectly symmetrical section was obtained. On each side the beds snapped, and a pair 

 of thrust-planes were produced, which buried themselves in the monoclinal folds of which 

 the whole fold is composed. 



After the limbs of the central anticline had been compressed till they met, a pair of 

 smaller arches were started by wedging up the waxcloth at either side. The central fold 

 was, on the application of the screw, squeezed upwards, and the beds becoming more 

 compressed exhibited the fan structure more conspicuously (figs. 20 and 20a). 



Fig. 21. 



On continuing the pressure, the three folds were still further compressed, and the 

 core of the central anticline was drawn upwards and considerably attenuated. A pair of 

 thrust-planes were formed on each side, and the beds forming the haunch of the main 

 arch were forced inwards above the lines of shear, so as to dip in an inverted position 

 towards the axis of the fold (fig. 21). 





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4HB 



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HM 



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Fig. 22. 



At this last stage of compression the development of a second and larger fan out- 

 side the first is clearly seen (fig. 22). Along the outer limbs of each of the folds the 



