ASYMMETRY OF THE NORTHERN HEMISPHERE 101 



The relations of the European mountain chains to the Atlantic ocean 

 are as follows : 



a. The chain of the western Mediterranean bends back by Gibraltar, 

 so that a continuation of the same into the ocean can not be assumed. 

 Such continuation would be only supposable for the great Atlas north of 

 Wady Draa. 



b. The folds which form the Spanish Meseta also betray, in the Astu- 

 rian basin, that they are bent back on themselves ; here also a continu- 

 ation for a long distance west can not be assumed. 



c. In relation to the possible continuation of the Pyrenees I do not 

 venture to express a suspicion, in spite of new and excellent investiga- 

 tions. 



d. The Armorican folds from La Rochelle to near the Shannon, wholly 

 in contrast to Gibraltar and the Meseta, run out into the sea as rias coasts 

 in such a way that their former continuation into the region which is 

 today covered by the ocean is in the highest degree probable. In fact, 

 the whole visible Armorican region is only the east end of a great and 

 broad curve, convex toward the north. It occurred for the most part 

 between middle and upper Carboniferous, but has since experienced 

 later ("posthumous") movements. It consists of several ^curved folds, 

 one behind the other. 



e. The pre-Devonian Caledonian folds, which strike southwest, have 

 such a position in the north and west of Ireland that their outer border 

 may meet the Armorican lines not very far west of the mouth of the 

 Shannon, perhaps to disappear under them, as the more easterly folds 

 of the same chain disappear, or, as in Moravia, the Variscan folds sink 

 under those of the Carpathians. 



/. Lewis and the western Hebrides, together with a small part of the 

 peninsula of western Scotland, form the foreland of the Caledonian folds, 

 and are simply the eastern border of a great Archean region which is 

 now covered by the sea and from which the significant quantity of clastic 

 sediments was derived which has caused the great thickness of the old 

 Paleozoic deposits in Wales and bordering regions. 



The Hebridian gneiss had certainly a greater western extension, as has 

 often been asserted by leading British geologists. 



From these facts the following tentative result is reached concerning 

 the relation of Europe to America and concerning the character of 

 the Atlantic region ; that the coast tracts, a (Gibraltar) and b (Meseta, 

 Asturian folds) clo not permit the assumption that their structure con- 

 tinues far westward ; that c (Pyrenees) and d (Caledonian folds) are un- 

 certain ; that, on the other hand, d (Armorican folds) and/ (Hebrides) 



XIV— Bum,. Geol. Soc. Am., Vol. 11, 1899 



