1848.] MURCHISON ON THE STRUCTURE OF THE ALPS. 249 



servations from the supposed centre of disturbance, become so mani- 

 fest in the outer group of the Hoher Sentis in the same longitude. 

 I am aware that there is a great difficulty in accounting for the lateral 

 folds and plications of the Alpine strata, from the supposed absence 

 of adequate central masses of erupted matter to dislodge, roll over or 

 compress into smaller horizontal areas, strata which must once have 

 been regularly extended in sheets. But might not the formation of 

 great central crystalline ellipsoids, whether eruptive or metamorphic, 

 serve in some measure to account for this ? May not these ellipsoids, 

 in being transformed and amplified, have operated as great centres 

 of mechanical force ? And with our knowledge of the position here 

 and there of very considerable masses of true granite, may not much 

 of that rock have acted without being visible, and may not large 

 masses of it be hidden under unfathomable glaciers ? 



But leaving this enigma, let us return to the consideration of the 

 lateral folds to which the strata of these mountains have been me- 

 chanically subjected. In them we learn not to be sceptical concern- 

 ing the truth of many sections in the Alps, such in particular as those 

 of M. Hugi, which represent rapid repetitions of Has and different 

 Jurassic formations in parallel sheets ; for we need only suppose the 

 superficial portion of narrow undulations removed by a powerful 

 denudation, and many of the phsenomena he represents would be 

 at once realized. 



I am happy to bring forward these few data at the present mo- 

 ment, when Professor H. Rogers, one of the authors of the undida- 

 tory or earthquake theory as applied to mountains, is in England, 

 and when he has taken the trouble to point out to me how some of 

 my facts may, as he thinks, be explained on his principles of illus- 

 tration. Putting aside his theory, we have only, indeed, to look at 

 the elaborate map of the Appalachian chain, by his brother and 

 himself, and witness the numerous ellipses into which the palaeozoic 

 masses have there been turned, and scan the sections of these authors, 

 based on positive data and outcrops of mineral masses worked for 

 use, in order to comprehend how the enormous faults and slides have 

 there occurred just where the strata have been most bent and in- 

 verted in reference to the centre of disturbance. Thus, the compa- 

 ratively low chain of North America may throw light on some of the 

 most complicated problems of our science, which could scarcely ever 

 have been satisfactorily worked out amid the confusion of the Central 

 Alps, such large portions of them being inaccessible to man and 

 covered with eternal snow. 



The inversion or the dipping of the strata towards the centre of a 

 chain, so as to place the older over the younger deposits, has been a 

 subject of wonder, and has hitherto been considered scarcely expli- 

 cable upon any satisfactory hypothesis. In viewing the Ural moun- 

 tains, where the same phsenomenon is copiously displayed, I was dis- 

 posed to account for such apparent inversion, by supposing that the 

 broken ends of the strata had fallen into abysses or cavities produced 

 by the extravasation of the enormous masses of igneously formed 

 rock, which are there seen at hand as if ready to explain the facts. 



