﻿Tlie Structure of Eur ope. 287 



It sometimes happens that in certain districts table- 

 lands break down, the subsidence occurring unevenly, 

 generally in streaks, wider or narrower, one streak sub- 

 siding more and another less. That portion which sinks 

 least, and which may frequently be observed standing out 

 in relief, is called a Horst. This horst has not been pro- 

 duced by upheaval, but owes its prominence to the 

 subsidence of the surrounding parts ; here, too, erosion 

 may act and remove the horst wholly or in part. Its 

 original structure can, however, easily be discoA-ered by 

 an ideal restoration of the separate strata. Such a horst 

 is called a table-horst. It may also happen sometimes 

 that mountain ranges break down, and then most compli- 

 cated relations are produced, and it- is one of the most 

 difficult problems of tectonic geology to discover in a horst 

 which has been produced in this way the original folded 

 mountain range. 



Look, for instance, at the stock of Morvan in Central 

 France, or the peninsula of Cot^ntin, on a geological map 

 of Europe. We see immediately that these are horsts, 

 and, moreover, fragments of folded mountain ranges 

 bounded by immense lines of fault. Closer examination 

 shows, however, that the strike of the folds has nothing to 

 do with the direction of the lines of fault. This is most 

 clearly seen where a folded horst is broken off' by the sea, 

 as, for example, in Southern Ireland, Cornwall and 

 Brittany. 



The comparison of these two concepts : table-land and 

 folded mountain range, table-horst and folded horst, with 

 this chronological table, is a complicated work which has 

 produced the general view regarding the structure of this 

 portion of the world. I will endeavor, as far as the hour 

 will allow, to give you a sketch of it. 



We see on the map various colors.^ The volcanic areas 



1 The lecture was illustrated with a colored map. The blue and red tones mentioned 

 in the lecture are replaced iu the figure by darker and lighter shading. 



