ICX) NEW YORK STATE MUSEUM 



Undoubtedly the obscurity which always surrounds the products of 

 deep-seated processes has in large part served to make the interpre- 

 tation of these rocks difficult. The tendency of earlier geologists 

 to see in the gneissoid structure evidence of sedimentary bedding 

 has also stood in the way of conceptions characteristic of later 

 workers. 



In outlining the Swedish Archcan we may establish therefore 

 at the outset that, 



1 It closed with a vast period of denudation. 



2 Back of this there was" a very important development of 

 granites which may be classed under four types. 



3 Back of the granites just referred to there is a great complex 

 of minor sediments and major deep-seated intrusives. 



To the time interval of erosion, reference has already been made. 

 The granites are widespread and of great interest. They are char- 

 acteristically massive. While Professor Hogbom makes four types, 

 Professor Tornebohm, on the map of the Swedish Geological Sur- 

 vey, distinguishes three groups, each wnth several subdivisions. The 

 four types of Professor Hogbom embrace (a) a coarse-grained 

 gray or reddish porphyritic granite, one of whose occurrences is 

 called the " Refsund " and was seen by the foreign visitors. It is 

 difficult to mention any familiar American occurrence that is 

 closely similar, (b) A fine to medium-grained gray or light reddish 

 biotite granite which is prominent in the city of Stockholm itself 

 where it was shown to the members of the Congress. The quarries 

 in Stockholm remind a visitor of Dix Island, Maine; Barre, Vt.; 



o 



and Westerly, R. I. (c) A true muscovite-granite in Angerman- 

 land which was not in the routes of the excursions, (d) Coarse 

 pegmatitic granite which we saw on the island of Uto. All of these 

 types are grouped by Professor Hogbom under the name Serarchean 

 or late Archean, a rather bad word etymologically, as it has a Latin 

 prefix (serus, late) to a Greek derivative, Archean. 



The members of the great complex, older than the granites just 

 mentioned, present an extremely difficult subject to set forth intelli- 

 gibly in a short space or even for a Swedish geologist of a life- 

 time's experience to make comprehensible. We may select, how- 

 ever, certain main features. 



Sedimentary rocks are represented by the usual types. There 

 are greatly compressed conglomerates, one of which was shown 

 to us near Malmbiick in southern Sweden. The pebbles of finely 

 crystalline rocks were pinched out to lenses and, while easily recog- 



