122 Professor Hoffmann on the Geology ofMassa Carrara. 



tion, we meet with, first, a dark grey compact or fine dolomitic 

 limestone, on which the whole mass of marble reposes, andocca- 

 sionally numerous layers and nodules of flint appear in the 

 Bardigllo-Yike limestone. In the upper part of the limestone 

 region of the Jpuanian Alp, we meet with numerous repetitions 

 and proofs of the relations described. It is only the pass over 

 the chain of the Tamhura which presents peculiarities. When 

 we have crossed the Tambura from the north-east, we leave, at 

 the bridge under Vagli di Sotto, the last trace of the Macigno 

 formation, which is cut through to this point from the valley of 

 the Serehio, viz. a fine granular sandstone. On the other side, 

 towards Vagli di Sopra, a compact dark limestone seems always 

 to occur again, a rock which is so often subordinate to the Ma- 

 cigno ; numerous veins of white, small, granular calcareous spar 

 traverse it, which soon predominate over the mass itself, and con- 

 vert it into marble. The numerous layers of slate in the mass of 

 the marble have always, towards the upper part, the character of 

 what Savi has called Galestro ; they are iron red, often also 

 green, and at the junctions of the layers there are the dull plates, 

 which generally occur in old clay-slates and secondary slaty 

 marls. Sometimes they contain more talc, become more shining, 

 and then resemble the old talc-slates ; sometimes they seem dull 

 and crumbling, so that one would be inclined to believe himself 

 transported to secondary rocks. Layers and nodules of jasper 

 are also not awanting. The marble, which is always so distinct- 

 ly divided into red beds on the great scale, is here everywhere 

 intimately connected with the layers of Galestro. It is inter- 

 ramified and interwoven with it. In the midst of the marble, 

 we meet with stripes and veins of rough vesicular limestone, 

 which passes into compact and into dolomitic limestone. At the 

 crest of the mountain chain lies a partly splintery, partly more 

 or less altered smoke-grey limestone, in which Guidoni found a 

 cast resembling a Turritella. Nearly the whole of the decHvity 

 of the Tambura chain towards the sea is decidedly dolomitic, 

 although very often the pure marble-like granular limestone 

 occurs in it. Under the Pizzo d'Uccello, the limestone is tra- 

 versed by veins of calcareous spar and quartz, and contains also 

 masses and layers of flint. Nearer Ajola, there are masses and 

 layers of a fine granular felspar, a kaolin-like substance, seldom 



