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western half they take a northeast and southwest direction. 

 The slate zones of the east take in general the form of 

 much elongated ellipses surrounded by quartzite, while 

 in the west the zones of quartzite are mostly elliptical 

 in shape, and they are surrounded by slate. The chief 

 difference between the structure of the east and that of 

 the west is that, in the east the folds are much more 

 tightly compressed, the strata in the east commonly 

 dipping at angles varying from 6o° to 90 , while those 

 in the west generally dip at lower angles. This is probably 

 due to the predominance of the thick, massive and inflexible 

 beds of quartzite in the west offering more resistance 

 to the pressure than the alternating thinner beds of quart- 

 zites and slate beds of the east. 



Along the anticlinal axes the strata lie in a series of 

 dome-shaped folds or "domes", the axes of folding pitching 

 alternately to the east and west. It has been thought that 

 these domes were produced by a second series of parallel folds 

 crossing the east and west series at a high angle. There is, 

 however, no such alignment of the domes in the east, though 

 in the west it does occur in some places where broad folds 

 or undulations are found here and there having a northeast 

 and southwest orientation, but generally only for short 

 distances. In Queens county there is an important trans- 

 verse anticlinal fold, producing a general doming of the 

 main anticlines and an extensive development of the quart- 

 zite. The result is that the lowest known beds of the series 

 are exposed at the surface. The compression that pro- 

 duced the pitching folds was probably contemporaneous 

 with that producing the long east and west folds and gene- 

 rally was local in its action. 



Whereas the anticlines are approximately parallel they 

 vary in length from a few miles to 100 miles (160 km.). 

 In some places two anticlines unite to continue as one, 

 several subordinate crumples being formed at the place of 

 union. In other places one anticline dies out only to be 

 succeeded a short distance north or south by another, or it 

 may be broken up into a series of short folds arranged 

 en echelon the whole combining to make one great fold. 

 Subordinate small crumples a few miles in length, on the 

 limbs of the main anticlines are exceedingly common, 

 particularly in the west, and more specially in the Halifax 

 formation. In this formation the slates, on account of 

 their more plastic nature crumpled into small folds more 



