KNOWLEDGE OF EARTH STRUCTURE 185 



The determination of plications to particular localities pre- 

 sents difficulties in the way of the contractional hypothesis which 

 have been underrated. It has been assumed that if a contraction 

 of the interior were to occur, the yielding of the outer crust 

 would take place at localities of least resistance. But this could 

 be true only on the assumption that the crust could have a hori- 

 zontal movement in which the nucleus does not necessarily share. 

 A vertical section through the Appalachian region and west- 

 ward to the 100th meridian shows a surface highly disturbed 

 for about two hundred and fifty miles, and comparatively undis- 

 turbed for more than a thousand. No one would seriously argue 

 that the contraction of the nucleus had been confined to portions 

 underlying the disturbed regions: yet if the contraction was 

 general, there must have been a large amount of slip of some 

 portion of the undisturbed segment over the nucleus. Such a 

 proposition would be very difficult to defend, even if the pre- 

 mises were granted. It seems as if the friction and adhesion of 

 the crust upon the nucleus had been overlooked. Nor could this 

 be small, even though the crust rested upon liquid lava. The 

 attempts which some eminent geologists have recently made to 

 explain surface corrugation by this method clearly show a neg- 

 lect on their part to analyze carefully the system of forces which 

 a contraction of the nucleus would generate in the crust. Their 

 discussions have been argumentative and not analytical. The 

 latter method of examination would have shown them certain 

 difficulties irreconcilable with their knowledge of facts. Adopt- 

 ing the argumentative mode, and in conformity with their view 

 regarding the exterior as a shell of insufficient coherence to 

 sustain itself when its support is sensibly diminished, the ten- 

 dency of corrugation to occur mainly along certain belts, with 

 series of parallel folds, is not explained by assuming that these 

 localities are regions of weakness. For a shrinkage of the 

 nucleus would throw each elementary portion of the crust into 

 a state of strain by the action of forces in all directions within 

 its own tangent plane. A relief by a horizontal yielding in one 

 direction would by no means be a general relief." 



Button's criticisms robbed the current hypothesis of 

 mountain-making of its conventional basis without pro- 

 viding a new foundation. It was a quarter of a cen- 

 tury in advance of its time, has been seldom cited, and 

 seems to have had but little direct influence in shaping 

 subsequent thought. It, however, gave direction to But- 

 ton's views, and his later papers were far-reaching in 

 their influence. 



If contraction from external cooling is not the cause 



