32 ROCK-METAMORPHISM. 



Hunt assumes that the rock is Archaean*. Setting aside the 

 question whether a specimen of the kind is of any value in 

 determining the age of a rockf, it may be mentioned that 

 Studer long ago discovered ammonites and belemnites in a 

 similar but less crystalline deposit, lying between gneisses, at 

 Mettenberg near Grindelwald, only a few miles (as the crow 

 flies) from MettenbachJ. 



Hoffmann expressed his astonishment on meeting, at Carrara, 

 with clay-slate, mica- and talc-schists and gneiss, not only fol- 

 lowing and alternating with saccharoid marble, but passing 

 into and blending with it intimately . This same marble, 

 which in many places contains or is associated with serpen- 

 tine, is of Carboniferous age, as is shown, from its fossils, by 

 Coquand and Cocchi. This is no case of " local alteration ;" 

 nor is it even pre- Carboniferous. But what shall we say of the 

 vast region stretching from Central Italy far into the " Dolo- 

 mites " of Tyrol, where similar metamorphosed rocks, con- 

 taining Triassic and Liassic fossils, are predominant ? 



It has long been known that in the Mont-Cenis district 

 there are beds more or less altered talc- schists, ophites, mi- 

 caceous limestones and saccharoid marbles, intimately asso- 

 ciated with beds containing belemnites and infra-Liassic fossils. 

 To those who are wedded to the " novel doctrine/' there is no 

 difficulty in their squaring even this case with it. Its author 

 states they "may correspond to the anhydrites which, with 

 gypsum, dolomite, serpentine and chlorite slate, are met with 

 in the primitive schists of Fahlun in Sweden "||. Conceiving 

 it to be tf improbable " for such rocks to be " of palaeozoic age," 

 as held by Gastaldi and others, he contends for the correctness 

 of his view, that they " are eozoic " U (Laurentian or Archaean) . 



But even should the infra-Liassic and Jurassic fossils, referred 

 to, be able to recover their inalienable right to stand as witnesses 

 in this case, it would not surprise us, from what may be gathered 



* Chemical and Geological Essays, p. 342. 



t Structures identical with those regarded as " eozoonal " have been dis- 

 covered by us. in ophite of Jurassic age in the Isle of Skye (see Proc. of the 

 Royal Irish Academy, n. s. vol. i. pt. 2). 



f Lehrbuch der Physikal-Geographie und Geologie, vol. ii. p. 158. 



Karsten's Archiv fiir Mineralogie, vol. vi. p. 258 j Bischof, op. cit. vol. 

 iii. p. 142. 



|| Chemical and Geological Essays, p. 336. 



f Ibid. p. 347. 



