614: AGE OF METAMORPHIC ROCKS. [Ch. XXXVH 



veins are observable, piercing through talcose gneiss, which passes insen 

 sibly upwards into secondary strata. 



It is certainly in the Alps of Switzerland and Savoy, more than in 

 any other district in Europe, that the geologist is prepared to meet with 

 the signs of an intense development of plutonic action ; for here we find 

 the most stupendous monuments of mechanical violence, by which strata 

 thousands of feet thick have been bent, folded, and overturned. (See 

 p. 58.) It is here that marine secondary formations of a comparatively 

 modern date, such as the Oolitic and Cretaceous, have been upheaved 

 to the height of 12,000, and some Eocene strata to elevations of 10,000 

 feet above the level of the sea ; and even deposits of the Miocene era 

 have been raised 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 geologists who 

 have explored the Alps, especially those of MM. De Beaumont, Studer, 

 Necker, Boue, and Murchison, 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 largo scale of secondary strata, containing fossils, with gneiss and 

 other rocks, of a perfectly metamorphic structure. I have visited some 

 of the most remarkable localities referred to by these authors; but al- 

 though agreeing with them that there are passages from the fossiliferous 

 to the metamorphic series far from the contact of granite or other plu- 

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

 tions 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 Bernese Alps, namely in the Both- 

 thai, a valley bordering the line of perpetual snow on the northern side 

 of the Jungfrau, there occurs a mass of gneiss 1000 feet thick, and 

 15,000 feet long, which I examined, not only resting upon, but also 

 again covered by strata containing oolitic fossils. These anomalous ap 

 pearances 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 superposi 

 tion, 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 con- 

 vulsions 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 conceive, be ascribed to me- 

 chanical 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 por- 

 tions 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 



