INDUSTRIAL PROGRESS DURING THE YEAR 1876. xcix 



with greenstones, ferriferous dolomites, red hematites, and copper 

 ores. These groups of metalliferous strata are much contorted, with- 

 out organic remains, and are conjectured by Pettersen to be either 

 of Silurian or Devonian age, though they liave the characteristics of 

 Huronian rocks. In other parts of Scandinavia the notion of altered 

 Paleozoic rocks is carried to a much greater extent, and, according 

 to Tornebohm, all the various types of crystalline Eozoic rocks, in- 

 cluding the granitoid gneisses, are reproduced again at a higher 

 horizon, the fossiliferous Paleozoic rocks which repose on the Eozoic 

 being supposed to pass beneath, and to be more ancient than this 

 second and newer set of crystalline strata. It remains to be seen 

 whether this is really the case, or whether this apparent superposi- 

 tion results from the same structure as has been described above in 

 the Appalachians. 



MARBLES OF CARRARA. 

 A similar question continues to occupy the geologists of Southern 

 Europe, where the crystalline rocks of the Alps, Apennines, and Pyr- 

 enees have been by different observers assigned to very different 

 horizons. The statuary marbles of Carrara arc an example of this. A 

 generation since they were looked upon as eruptive ; then, together 

 with their associated crystalline schists, they were declared to be al- 

 tered Cretaceous. They were subsequently referred to the Lias, until 

 shown to be unconformably overlaid by Liassic strata and to rest in dis- 

 cordant stratification on crystalline schists, when they were assumed 

 to be altered strata of Rha^tic age. Later observations placed them 

 beneath the coal-measures, and the Carrara marbles were then called 

 Lower Carboniferous, to which horizon some have also referred all 

 the statuary marbles and micaceous limestones of Central Italy. 

 Similar statuary marbles in the Pyrenees, formerly regarded as alter- 

 ed Mesozoic, are now considered to be Carboniferous, or still older. 

 According to Gastaldi the marbles and micaceous limestones of Italy 

 just referred to are still more ancient, and are closely related to the 

 Pietre verdi group ; so that their position, if not pre-Paleozoic, is at 

 the very base of the Paleozoic series. 



CRYSTALLINE ROCKS OF ITALY. * 



The name of the Pietre verdi or greenstone group, is given in Italy 

 to a widely spread series of stratified rocks of great thickness. It 

 consists, to a large extent, of rocks with triclinic feldspars the so- 

 called gabbros and diabases together with great masses of serpen- 

 tine, and diallage, and steatitic, chloritic, and epidotic strata, the 

 whole associated with quartzose and calcareous schists. These rocks 

 have been by most geologists looked upon either as eruptive or as 

 contact-deposits resulting from the action of eruptive masses upon 

 uncrystalline strata, and have been assigned, from their supposed 



