298 



LYELL'S ELEMENTS OF GEOLOGY. 



Age of Metaraorphic Rocks of the Swiss Alps. 



date, such as the oolitic and cretaceous, have been upheaved to 

 the height of 10,000, or even 12,000 feet above the level of the 

 sea ; and even tertiary strata, apparently of the Miocene era, 

 have been raised to an elevation of 4000 or 5000 feet, so as to 

 rival in height the loftiest mountains in Great Britain. 



If the reader will consult the works of many eminent geolo- 

 gists who have explored the Alps, especially those of MM. De 

 Beaumont, Studer, Necker, and Boue, he will learn that they all 

 share, more or less fully, in the opinions above expressed. It 

 has, indeed, been stated by MM. Studer and Hugi, that there are 

 complete alternations on a large scale of secondary strata, con- 

 taining fossils, with gneiss and other rocks, of a perfectly meta- 

 morphic structure. I have visited some of the most remarkable 

 localities referred to by these authors, but although agreeing with 

 them that there are passages from the fossiliferous to the meta- 

 morphic series far from the contact of granite or other plutonic 

 rocks, I was unable to convince myself that the distinct al- 

 ternations of highly crystalline, with unaltered strata above 

 alluded to, might not admit of a different explanation. In one 

 of the sections described by M. Studer in the highest of the Ber- 

 nese Alps, namely in the Roththal, a valley bordering the line 

 of perpetual snow on the northern side of the Jungfrau, I observ- 

 ed a mass of gneiss 1000 feet thick, and 15,000 feet long, not 

 only resting upon, but also again covered by strata containing 

 oolitic fossils. These anomalous appearances may partly be 

 explained by supposing great solid wedges of intrusive gneiss to 

 have been forced in laterally between strata to which I found 

 them to be in many sections unconformable. The superposition, 

 also, of the gneiss to the oolite may, in some cases, be due to a 

 reversal of the original position of the beds in a region where 

 the convulsions have been on so stupendous a scale. 



On the Sattel also, at the base of the Gestellihorn, above 

 Enzen, in the valley of Urbach, near Meyringen, some of the 

 intercalations of gneiss between fossiliferous strata may, I con- 

 ceive, be ascribed to mechanical derangement. Almost any 

 hypothesis of repeated changes of position may be resorted to 

 in a region of such extraordinary confusion. The secondary 

 strata may first have been vertical, and then certain portions 

 may have become metamorphic (the plutonic influence ascending 

 from below) while intervening strata remained unchanged. The 

 whole series of beds may then again have been thrown into a 

 nearly horizontal position, giving rise to the superposition of 

 •crystalline upon fossiliferous formations. 



It was remarked, in the last chapter, that as the hypogene 

 rocks, both stratified and unstratified, crystallize originally at a 



