Be R. T. CHAMBERLIN AND W. Z. MILLER 
outlines of the prepared block, by exaggerating any case of piling 
up likely in nature, ought not to fail to reproduce the low angles, if 
such be due to piled-up material acting in this way. The results 
are shown in Figs. 12 and 13. ‘There was first slice faulting on the 
right-hand side, from which the pressure came. Each successive 
fault broke below the previous one as the mass was compressed 
more and more. This is similar to the experience of Cadell. As 
compression went on, the planes of the earlier faults became 
Fic. 13.—Same as Fig. 12. After further compression 
distorted and obscured by the later deformation. At length a low- 
angle fracture broke through from the left, or resistance block side. 
This was no doubt determined by lines of least resistance due to 
weakening by the previous fracturing. 
To test the matter further a mold of pure paraffine was pre- 
pared in essentially the same shape. The paraffine had the advan- 
tage of being more nearly homogeneous than the clay-plaster 
combination. In the two trials made, fracturing proceeded directly 
across the elbow at approximately 45° (Fig. 14). Lest the right- 
angled elbow might play an unsuspected part in determining the 
angle of splitting, paraffine was molded into a block having the 
shape shown in Fig. 15. When pressure was applied the block 
faulted at the farther end. It faulted at the farther end because 
