348 THE JOURNAL OF GEOLOGY. 



ranges come together at their extremities are difficult to explain 

 by it. It may be said in this connection that the dip observa- 

 tions toward the west are not so satisfactory or numerous as they 

 might be." The question naturally arises whether or not the 

 great width of the ranges in the central part of the area may 

 not be partly explained by monoclinal faulting, and thus reduce 

 the supposed thickness of the beds. 



The layers of quartzite are ordinarily very heavy, but the 

 changing character of the original sediment is such as to make 

 it easy to follow the layers. Some beds were composed of fine 



f 



Nfiyth flang^ /' ,' ,^'' ,'' ^'' SpoAh Yla.-n'g'e 



Fig. I. — Ideal Sketch, showing structure and amount of erosion of the Barboo Ranges. 



After Irving. 

 Scale natural, i2,ooo feet to the inch. 



grains of quartz, mingled with clayey material, others of coarse 

 grains with little clayey material, and others of pebbles so large 

 as to pass into an unmistakable conglomerate. The pebbles of 

 the conglomerate are mainly white quartz and red jasper. It is 

 thus easy to discriminate the bedding of the series from the 

 heavy jointing which occurs, cutting the bedding in various 

 directions, and from a secondary cleavage and foliation which 

 occurs in certain localities. 



From the general work of many geologists on dynamic 

 action in folding, it is to be expected that the amount of move- 

 ment necessary for accommodation between beds, and conse- 

 quently the dynamic metamorphism resulting from shearing, 

 would be less near the crown of the anticline than on the leg of 



