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the axis planes, whether they are comcident with them or not. 

 Many of the more extensive longitudinal dislocations of the Appa- 

 lachians are traceable to the rupturing of the anticlinals along their 

 most wrenched inverted slopes. These waves are entire at their 

 extremities, but so broken along all their intervening portions as to 

 present only one-half of the wave form, the other half being pro- 

 foundly buried with inversion under the unbroken part. Gene- 

 rally, in these great dislocations, the gently-dipping uninverted slope 

 of the waves has been shoved — in the inclined plane of the fault — 

 forward and upward upon the other inverted and crushed half, and 

 in some instances through a great distance. 



The up-driven parts having been extensively removed by erosive 

 action, the upper strata of the overturned buried half of the wave 

 are seen to be immediately overlapped in nearly conformable altitude 

 of dip by the denuded lower strata of the uninverted side. Similar 

 phenomena of the plunging of newer formations under older ones, 

 with approximately conformable dips, meet us continually in the Alps, 

 and other much plicated districts, and can be demonstrated to have 

 arisen from the same cause, the upward and forward propulsion of 

 the uninverted halves upon the inverted sides of the anticlinal waves 

 along the great sloping planes of dislocation, into which the flex- 

 ures have snapped at the time of their sudden bending. 



These several laws of crust undulations, consisting of those which 

 relate to the parallelism, form, gradation in distance, shape, and 

 dislocation of the waves, are exemplified in detail in the paper, and by 

 appeals to the phenomena of some of the more conspicuously corru- 

 gated tracts of Europe. Viewing, as one such zone, the undulated 

 districts of southern Belgium, the E-henish Provinces, the West- 

 phalian coal-field, the chain of the Ardennes, and the Hundsruck, 

 Taurus, and Hartz ranges, and referring for proofs to the descrip- 

 tions and maps of M. Dumont and other geologists, who have described 

 these provinces in more or less detail, the author shows that this 

 •belt displays all the phenomena of structure and gradation described 

 by him as so conspicuous in the Appalachians of America. Sections 

 transverse to this region from S.E. to N.W. will be found to exhibit 

 precisely the same succession, from closely folded flexures with 

 metamorphism through steep normal waves, to broad, open, and 

 approximately symmetrical ones. 



