68 PROC. COTTESWOLD CLUB vol. xili. 



which flank it on either side and forms part of the massif 

 of the Apennines, altered as that central nucleus has been 

 in the Alps. 



The fact, however, remains that whether the schists are 

 of Carboniferous, Palaeozoic or Archaean age, they are so 

 much altered that as yet undoubted evidence of their 

 position in the geological series is still wanting. And if 

 any Cotteswold geologist would visit this interesting 

 district and carefully map down the faults, note the great 

 crushes, and follow up the strata from the flanks on either 

 side to the central nucleus, he would pass a pleasant and 

 profitable time amongst the picturesque valleys and 

 glorious scenery of these marble mountains. 



As to the alteration of the limestones, of whatever date, 

 into their present crystalline form, here, again, opinions 

 difl'er. That a metamorphosis has taken place all agree ; 

 some attribute this to igneous action, but there is no 

 evidence of this in the Carrara district. The yellow, 

 streaky, veined Sienna marble may have been formed by 

 the intrusion of igneous rocks, as veins of Serpentine are 

 not uncommon there ; but in our visit we saw no indica- 

 tion of any intrusive dykes, and M. Jervis says that 

 evidence of igneous action in the Carrara mountains, 

 consisting of marble 3000 feet high, is singularly wanting. 

 An intrusion of Serpentine does, however, appear near 

 Spezzia, I have since ascertained. 



The crystalline, granular, saccharoidal structure of the 

 marble requires, according to the best authorities, heat 

 and pressure, aided by moisture. Geikie writes : " The 

 conversion of wide areas of limestones into marble 

 is a regional metamorphism associated usually with the 

 alteration of other sedimentary masses into schists, 

 &.C." (Text Book, 1882, p. 304.) M. Jervis thinks that 

 metamorphism of sedimentary rocks, without the inter- 

 vention of intense heat from the redistribution of the 



