i86 OUTLINES OF FIELD-GEOLOGY PART 1 



materials there is generally no room for doubt. But 

 on examination, it is found that the pebbles in the con- 

 glomerates have often been crushed, flattened, and even 

 pulled out of shape, while the original sandy or gravelly 

 matrix has become a crystalline schist (Fig. 72). But 

 that is not all. We may observe that the pebbles have 

 been pulled round in one general direction (l-'ig. 73), 

 and that this direction is that of the foliation. Prom 



FIG. 73. Bds of conglomerate and schist. Shore, Catacol, Isle 



The pebbles in the conglomerate (c) have been moved round and placed with 

 their longer axes in the plane of foliation (indicated by the arrow) which 

 is oblique to the bedding of the schists (*). 



such structures the conclusion must obviously be drawn 

 that the rocks have been subjected to enormous lateral 

 pressure, that their component materials, as in cleavage, 

 have been forced to rearrange themselves perpendicular 

 to the direction of the pressure, and that a crystallisation 

 of the crushed material has taken place along the planes of 

 shearing or cleavage, which has resulted in the production 

 of the foliated structure. 



But it is not only in sedimentary rocks that this re- 

 markable transformation may be seen. If the observer 



