280 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 
mentary origin represents a departure from the uniformity of condi- 
tions of later geological times.” ! 
Turning to the pre-Cambrian geology of other parts of the World we 
find that the Torridonian and Lewisian of northwest Scotland in 
their mutual relations and petrographical characters resemble the 
Algonkian and Archean divisions of North America. The aggregate 
thickness of the Torridonian has been estimated at not less than 
10,000 feet. To this the Dalradian has, possibly, to be added. 
The pre-Cambrian rocks of Finland have been divided by Sederholm 
as follows: 
Jotnian. 
Jatulian, Upper. 
Jatulian, Lower. 
Kalevian, Upper. 
Kalevian, Lower. 
Bottnian. 
Ladogian. 
Katarchean. 
Sederholm makes the same statement regarding the Jotnian, 
Jatulian, Kalevian, and Bottnian as has been made with reference to 
the Algonkian. Sederholm says: 
At least as far back as during Bottnian time the climatic conditions were not sensibly 
different from those of later geological periods, as shown by the’existence of rocks which, 
in spite of their metamorphic character, show themselves to be sediments with the 
same regular alternation of clayey and sandy material (annual stratification) as the 
glacial clays of that same region, explainable only by assuming a regular change of 
seasons.” 
The parallel suggested by Sederholm with the Lake Superior rocks 
is as follows: 
Jotnian equivalent to Keweenawan. 
Jatulian equivalent to Animikian or Upper Huronian. 
Kalevian equivalent to Lower Huronian. 
Van Hise and Leith further suggest the correlation of the Ladogian 
and Katarchean with the Kewatin and Laurentian; the Ladogian 
being intruded by the granites and gneisses of the Katarchzan. 
Tn China a basal complex of gneisses having very subordinate masses 
of sedimentary materials underlie four sedimentary groups, originally 
muds, grits, conglomerates, and limestones; having, in fact, all the 
characteristics of the Algonkian. In short this prevailing relation 
of an older gneissic and dominantly igneous system with an uncon- 
formably overlying metamorphosed sedimentary and _ volcanic 
1 Van Hise and Leith, loc. cit., p. 30. 
2 Sederholm, J. J., Bull. Comm. Gé6ol. de Finlande, No. 23, p. 95, 1907. 
