In those regions in northern Europe where Precambrian rocks prevail—that is, in the territory which comprises great parts of Scandinavia, all of Finland, Russian Carelia, and the Peninsula of Kola, and which is now generally called Fennoscandia—the main interest of the geologists studying the Precambrian rocks has long been focussed on the investigation of the older, crystalline parts of this complex; consequently, mainly petrological methods have been used. These rocks are here also the richest ore-bearers, not, as in North America, the rocks of Proterozoic or Huronian type. Rocks similar to the latter, for the study of which stratigraphical methods are applicable, are also found, however, in Fennoscandia, in its eastern and northern parts, where especially Finnish geologists have studied them, and also on the Russian side of the boundary. The central position of Finland and the circumstance that it is here that the sedimentary formations in . . .