DYNAMICAL GEOLOGY. 309 



Hungarian mountains, was introduced between the central 

 Alps and the southern zones. Professor Suess then demon- 

 strated a similar unilateral structure for the Balkan, Caucasus, 

 and Ararat mountains, and in all cases ^ the action of the 

 tangential forces had been from south to north. 



Hence a surprising similarity was demonstrated between the 

 mountains of Europe and those in North America which had 

 been described by Rogers and Dana, and the theory of 

 lateral compression so widely accepted by American geologists 

 seemed applicable to European mountain-chains with but few 

 modifications. Elie de Beaumont's method of determining 

 the ages of the mountain-chains was clearly unsuitable 

 upon this new conception of their structure. According to 

 Professor Suess, the tectonical disturbances which gave form to 

 the present Alpine system had begun in the Mesozoic period, 

 and had continued not only to the close of the Miocene time, but 

 (at least on the southern slopes) into the Pliocene and possibly 

 even the Diluvial Age. In considering the actual lines of 

 deformation, Suess pointed out that allowance must be made 

 for the retaining influences exerted by neighbouring immovable 

 mountain-blocks, by ancient intruded and interbedded volcanic 

 rocks, and by the resistance of the rock-folds themselves. 



A study of the older mountain-masses (afterwards called 

 " Horsts" by Suess) limiting the Alps on the west and north, 

 showed that the same direction of force which had folded the 

 Alps had also determined the structure of the Riesen moun- 

 tains, the Sudeten mountains, the Bohemian forest, the Harz, 

 the Ardennes, etc., and that this Central European mountain- 

 system of high geological antiquity had, like the later Alpine 

 system, been compressed by horizontal forces acting towards 

 the north-west, north, or north-east. Although in Europe as 

 in North America, the dominating direction of pressure had 

 come from the south, there were also evidences of compres- 

 sion towards the south. Val Sugana in the southern Alps, 

 Istria, Dalmatia and the Karst, the Ifer mountains, and 

 the Teutoburg forest were mentioned as types of southward 

 compression. Yet so prevalent was the northern direction 

 of movement over vast regions between the Caspian Sea and 

 the American shores of the Pacific Ocean, that one might 

 feel tempted to deduce a general streaming of rock-material 

 towards the North Pole throughout the whole Northern 

 Hemisphere. But several facts contradicted such a con- 



