:!42 ME CADELL ON EXPERIMENTAL RESEARCHES IN MOUNTAIN BUILDING 



strata below the fault plane, the shearing ceased, and the forward motion was temporarily 

 arrested. The photograph taken at this stage is reproduced in fig. 1. 





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Fig. 2. 





Fig. 2a. 



A new mass of strata was now brought under the influence of the pressure. In this 

 case the beds were subjected to a certain amount of vertical pressure due to the heaping 

 up of the strata on the slope of the wedge, in addition to the horizontal thrust from the 

 right. The resultant shear plane might therefore be expected to meet the fixed sole at a 

 slightly lower angle than before. An inspection of fig. 2 will show that this has been 

 the case. The upper reversed fault is slightly steeper than the lower. Much importance 

 is, however, not to be attached to this difference in hade, as the weight of the piled-up strata 

 in such experiments is small in comparison with the horizontal force, and slight differences 

 in the hade of successive reversed faults might be due to other causes. Fig. 2a is a dia- 

 grammatic representation of fig. 2, which is not very clear. 



Fig. 3. 



Fig. 3«. 



In this case (fig. 3) the depth of strata was only if inches. The breadth was 8 inches, 

 and the section was pressed in from an original length of 44 inches to a space of 15 inches. 

 The same process went on here as in last experiment, but the cumulative effect is better dis- 

 played. A small overfold produced at the beginning of the experiment may be seen at the 

 top of the section, but afterwards the strata underwent a process of piling up in separate 

 slices by slightly-inclined reversed faults. The back part of the accumulating mass 

 slipped vertically up the face of the pressure board as each new wedge was driven under 

 the base of the slope in front. Fig. 3a is a diagrammatic representation of this structure. 



These structures arc almost identical in character with the structures found in advance 



