C GENERAL SUMMARY OF SCIENTIFIC AND 



stratigraphical relations, to very different geological ages. Accord- 

 ing to Lory they are Triassic, while within the past year some have 

 been found closely associated with Silurian or Devonian fossiliferous 

 strata. De Stefani assigns certain of them to a horizon between the 

 Carboniferous and the Lias, others of them he refers to the Cre- 

 taceous, and others still are stated by him to overlie the middle and 

 lower Eocene. Gastaldi has, however, recently reviewed the whole 

 subject, and concludes that the rocks of the Pietre verdi are not 

 eruptive but indigenous, and constitute a well-defined series of beds 

 and lenticular masses, of great thickness, in which the serpentines 

 occupy a position near the base. The Pietre verdi has, according to 

 him, a constant and well-defined horizon, which is pre-Paleozoic, and 

 its rocks never make their appearance in other formations. This 

 formation, which has all the characters of the Huronian, to which he 

 has provisionally referred it, rests unconformably upon a great series 

 of gneissic rocks, often porphyroid and granitoid, which include de- 

 posits of graphite, beds of quartzite, lenticular masses of white statu- 

 ary marble, and doubtless represent the Laurentian. Overlying the 

 Pietre verdi is another great series of quartzites, and schistose lime- 

 stones and dolomites, including beds of gypsum near the summit. 

 These groups of ancient crystalline strata, according to Gastaldi, 

 constitute the basal rocks of the Alps and Apennines, and may be 

 followed from Mont Blanc to the Danube, the Adriatic, the Mediter- 

 ranean, and to the plains of France, overlaid in part by newer strata. 

 These views are in accordance with those maintained by Favre and 

 many others, who have shown by repeated instances that the ap- 

 parent interstratification of older among newer rocks in these regions 

 is due to inversions and dislocation. The w^riter, some years ago, 

 from his studies of Alpine geology, was led to maintain the view de- 

 fended by Gastaldi, and asserted the Eozoic age of these crystalline 

 rocks, including the Pietre verdi, 



CAMBRIAN ROCKS OF EUROPE. 



Hicks has discussed the different conditions presented by the Cam- 

 brian and Siluro-Cambrian rocks in Wales, where they have a united 

 thickness of 30,000 feet, and in Scandinavia and Russia, where they 

 are 1000 feet or less. He supposes them to have been deposited 

 over a slowly subsiding continent of Eozoic rocks, the surface of 

 which sloped toward a deep ocean to the southwest, and in accord- 

 ance with this view concludes that the earlier members of the Cam- 

 brian below the Menevian horizon are wanting in Scandinavia, which 

 was not submerged till then. To this Linnarsson objects, maintain- 

 ing: that both the Menevian and the fossiliferous Harlech strata, 

 which underlie it in "Wales, are represented by the Paradoxides 

 beds of Scandinavia, where below these are still recognized two dis- 

 tinct horizons of Paleozoic sediments, the Fucoidal sandstone and 



