THE PROTEROZOIC ERA. 215 



centers of sedimentation, as to correspond. r Igneous rocks form a 

 not inconsiderable part of the Proterozoic systems, and there is no 

 law requiring igneous activities in different regions to correspond 

 either in time or in the nature of their products. Even body defor- 

 mations, which are much the most general and which are the basis 

 for the subdivision of the systems, need not have corresponded in 

 their particular phases, in different regions. It follows (1) that the 

 number of series within the Proterozoic in one place may not be the 

 same as in another; (2) that the thicknesses of the various systems 

 may vary within wide limits; (3) that there need have been no close 

 correspondence in the sorts of rock in different regions at the outset; 

 and (4) that they may have been metamorphosed unequally since 

 their deposition. The dissimilarity of the . Proterozoic in different 

 regions, as suggested by the preceding sketch, was, therefore, to have 

 been anticipated. 



Proterozoic Formations in other Continents. 



' Little need be said of the Proterozoic systems of other continents, 

 but they are believed to exist in Great Britain, 1 where the Torridonian 

 sandstones (8,000-10,000 feet thick in Scotland) and perhaps the 

 Dalradian series may be Proterozoic; in France, 2 where phyllites, 

 graywackes, quartzite, sericitic schists, and igneous rocks with an aggre- 

 gate thickness of several thousand meters, are regarded as Proterozoic; 

 in Spain, where phyllites, halleflinta, and quartzite represent the era; 

 in Germany, where mica schists predominate below, and phyllites 

 above; 3 in Finland, 4 where nearly 3000 meters of conglomerates, quartz- 

 ites, schists, limestone, and diorite lie between the Archean and the 

 Cambrian; in Scandinavia (Sweden), where there are similar thicknesses 

 of similar rocks occupying a similar stratigraphic position; and probably 

 in India and Brazil. In more than one of these countries, the pre- 

 Cambrian sedimentary rocks are thought to belong to at least two 



1 Sir Archibald Geikie, Jour, of Geol., Vol. I, and Text Book of Geology, 4th ed., 

 Vol. II. 



2 DeLapparent, Traite de Geologie. 



3 Giimbel, Grundziige der Geologie, pp. 511-522. 



4 Sedersholm, Ueber eine archaische, Sedimentformation in siidwestlichen Fin- 

 land, Bull, de la Commission Geologique de la Finlande, No. 6, 1897. 



