456 HISTORICAL GEOLOGY. 



ARCHAEAN TIME IN OTHER COUNTRIES. 



South America has its northern region of Archaean rocks between the 

 equator and the Orinoco, which would probably have a much larger super- 

 ficial area but for the great alluvial and Tertiary area of the Amazon and 

 other rivers, which bound it for 150 miles on the north and two to three 

 times this width on the west. Archaean ranges also occur in Brazil, and in 

 different parts of the chains of the Andes. 



In the continent of Europe the great Archaean region is the Scandinavian^ 

 or that covering the most of Sweden, Norway, Lapland, and Finland. The 

 rocks also occupy a large part of the northern half of Scotland and the Outer 

 Hebrides ; portions of western Ireland, at Donegal and Gal way, and of 

 eastern, in Wicklow ; at St. David's, in southwest Wales ; in Anglesey, off 

 northwest Wales ; in western England, in the Malvern Hills ; and probably 

 on the south coast of Devon and Cornwall. They also cover areas in 

 Saxony, Bavaria, and Bohemia; in Brittany, Vosges, and the Central 

 Plateau of France. 



Crystalline rocks cover, according to Blanford (1879), very large areas 

 in India. " More than half of Peninsular India is taken up by the eastern 

 gneissic series." They extend, with scarcely an exception, from Cape 

 Comorin to Colgong on the Ganges, 1400 miles. The mean breadth of 

 the area is 350 miles. There are also in the peninsula a northwestern 

 area, the Arvali ; and, to the north of the Vindhyan plateau, the Bundel- 

 khand area. But it is not certain that all are Archaean. Besides these, there 

 are also large areas of semi-metamorphic rocks. The main Himalayan 

 range has a gneissic or granitic axis, but the limits are not yet laid down ; 

 and in the Zanskar range, its continuation to the northwest, there is a 

 center of gneiss. But the precise relations of these and other gneissic 

 ridges to the later formations has not been ascertained. 



The rocks of Scotland, Norway, Sweden, and other Archaean regions are 

 much like those of North America in general constitution, and in the range 

 of the associated minerals ; and in Scandinavia there are great iron ore beds. 

 The massive gneisses of the Hebrides and northern Scotland were called the 

 Lewisian group by Murchison (1858), after the island of Lewis in the Outer 

 Hebrides. Like the massive and the thick-bedded or foliated rocks, which 

 contain the iron ore beds of Scandinavia, they have been pronounced on 

 petrological grounds to be of igneous origin. But, for reasons already 

 stated, they are in all probability, wherever igneous, metamorphic-igneous, 

 or the result of fusion attending metamorphic work. The foliation of the 

 gneisses and other rocks represents, in general, on this view, true bedding. 

 The iron ore beds are the best of evidence of metamorphism. The crystal- 

 line rocks east of the " Great glen " in Scotland include thin schists and 

 quartzyte with gneiss, and have been called the Grampian group by 

 H. Hicks, and later the Dalradian group by Geikie ; it is supposed to be 

 younger than the Lewisian. 



