ORIGIN OF FRACTURES AND FAULTS. 725 



southwest of New York ; and there is no evidence that this differ- 

 ence is attributable to a difference of age. 



While the plications of the rocks of New England are in the 

 main nearly north-by-east in course, as shown by the strike of the 

 rocks, there is a region in southern Connecticut where the strike is 

 transverse to this direction, or parallel to Long Island and the 

 course of the Appalachians in Pennsylvania ; from which it may be 

 inferred that, cotemporaneously with the action of forces from the 

 eastward producing the prevailing plications of New England, a 

 force was also acting from the southward, or at right angles to its 

 southern coast. The complexity of directions in the White Moun- 

 tains may not be owing to a difference of age, but to the combined 

 action of forces from these two directions. 



13. The theory here adopted not in the main hypothetical. — In attri- 

 buting the plications of the earth's crust and the elevation of most 

 mountains to a lateral pushing movement or tension within the 

 crust, there is nothing that is hypothetical. The statement is the 

 expression simply of a fact. The conclusion that this tension is 

 due to the contraction of a cooling globe has not yet been fully 

 established. It is here adopted because no other that is at all 

 adequate has been presented. The cause must have been one 

 which would have produced an increasing amount of tension 

 through the passing periods, causing oscillations of the crust and 

 minor uplifts in the course of those long periods, and then a 

 great catastrophe, or an epoch of plications, metamorphism, and 

 grander uplifts, as a result of the great increase ; then another 

 slow increase and another catastrophe ; then others ; and a series 

 of similar but more or less independent catastrophes in distant 

 parts of the globe, raising, as late as the Tertiary period, many of 

 the earth's great mountain-chains, — but one which should cause 

 only minor oscillations and uplifts in more recent times, since the 

 earth has now a degree of stability unusual in the past ages (p. 586). 

 And no cause answers to these demands, so far as known, but 

 the one mentioned, — the contraction of a cooling globe. 



2. FRACTURES, FAULTS, AND STRUCTURAL PECULIARITIES. 



1. Fractures. 



The following are some of the causes of fractures : — 

 1. Drying through the heat of the sun, as in the formation of 

 cracks in mud or earth. — Such cracks are usually but a few 

 inches deep, — though in the soil of some prairies they occasionally 



