FOLDS AND FAULTING: A REVIEW. 



PART I. 



rO those who are interested in the deep and complex 

 problems geology is called upon to solve, the trien- 

 nial geological congresses afford a special means of obtain- 

 ing fresh light and knowledge, under the guidance of leaders 

 whose life-work has been carried out in the country, the 

 structure of which they are called upon to explain. Men 

 holding the most varying views are brought to examine the 

 same facts from their different standpoints, and the dis- 

 cussions which result from their contact lead to conclusions 

 of permanent value and wide-spreading influence. 



The meeting of the latest congress at Zurich, the sub- 

 sequent traverses across the Alps, and the publication of 

 the Livret-guide explanatory of these excursions, have 

 directed the minds of a large number of geologists to those 

 movements of the earth's crust, which have given rise to 

 that splendid range of mountains, whose detailed structure 

 and scenery we were called upon to examine. 



In the earlier part of the century the most varied 

 theories had been enunciated in regard to these inequalities 

 of the earth's surface, the facts of mountain structure being 

 little understood. Volcanic agency was made largely re- 

 sponsible for these upheavals ; the wedge-like intrusion of 

 igneous masses, the liftings of an internal igneous nucleus, 

 or the sinking of the ground by the removal of volcanic 

 material, being all called into requisition to account for the 

 phenomena. Simple upward pressure stood in sharp 

 contrast to horizontal or lateral compression, and around 

 these rival standpoints raged a combat not less severe 

 than those which in later years have divided the geological 

 world. 



The conceptions which have in the last decade gained 

 the ascendency in all probability first had their rise in the 



