SUESS' METHOD OF IXTERPEETATION 189 



the mountain ranges were produced hy tangential or horizontal thrusts 

 acting in a general way from northerly to southerly directions. 



'No other method of studying the products of diastrophism or earth- 

 deformation with the object of learning their causes gives an3^thing like 

 so much promise of final success as this^ for none takes hold in such a 

 broad, deep way. Suess' method is adapted to include and comprehend 

 the broadest possible relations and aspects of the phenomena of crustal 

 deformation. The facts dealt with by this method are not a more or 

 less unrelated aggregation of minuticT, as is too often the case with col- 

 lections of outcrops and cross-sections ; their scope and breadth are com- 

 mensurate with the extent of the mountain ranges themselves or even 

 with that of whole continents. Indeed, it is one of the objects of the 

 present paper to endeavor to show that the method of Suess is applicable 

 not merely to Asia and Eurasia, but to the whole northern liemisphere 

 and to the southern hemispliere also, and hence to the whole earth ; and 

 finally, that the conclusions reached by a broad application of this method 

 point even now very clearly to the general nature of the processes which 

 have produced the earth's plan. 



After noting the advances made by Reyer and Bertrand in tlie methods 

 of study of mountain ranges in transverse section, Suess makes the fol- 

 lowing remarks on the value of his own synthetic method: 



"A study of the mouutain chains in transverse section is, however, only one 

 {)art of our tasli ; we must also investigate them in horizontal projection — 

 that is, in plan. There was a time when every single anticline of the Jura 

 was regarded as an independent axis of elevation; then it became clear that 

 such a collection of parallel anticlines must have a common origin ; next it 

 was seen that there is a certain dependence between the Alps and the Jura ; 

 finally, the influence of the obstacle presented by the Black Forest was recog- 

 nized, and it became evident that the Alps and the Jura were only parts of the 

 southernmost, innermost, and most recent of three crescentic systems of folds 

 which have arisen one after the other across central Europe since the close of 

 the Silurian epoch. Thus with our increasing knowledge we are led to the 

 conception of units of a continually ascending order, and the several anticlines 

 of the Jura now appear to us as parts of an organic whole. 



"To continue this method of synthesis, to group the folded ranges together 

 in natural units of a still more comprehensive character, and to explain by 

 means of a single simple expression as large a part as possible of the terres- 

 trial folding — such is the task which now awaits the geologist. The plan of 

 the trend-lines, written by nature on the face of the earth — this it is which he 

 has to determine" (III, 3). 



In the present paper Suess' method of interpretation from the trend- 

 lines of mountain ranges is followed throughout, and is extended to the 

 largest possible units. But his conception of the manner of deformation, 



XIY — Bull. Gkol. t>oc. Am.. Vol. 21. inoo 



