REPORT OF THE DIRECTOR I9IO IO3 



eastern coast in the district of Nordingra that reminded the writer 

 very strongly of the American rocks. In Norway both the anortho- 

 sites and basic gabbros appear and with them are the syenitic series 

 of the New York geologists (mangerites of the Norwegian ob- 

 servers) as Professor Gushing made clear some years ago (13). 



Along the southeastern coast of Sweden between Stockholm and 

 Vastervik the visitors were shown phenomena that were new to the 

 greater number of us. Innumerable islands dot the coast; they 

 have been smoothed and polished by the great ice sheet until over 

 widths of 10 to 20 yards along the shore the ledges appear as if 

 prepared by a lapidary. Two rock magmas, a gabbro and a granite, 

 are intermingled in the most intimate way. In the ledges visited 

 by us, the granite had habitually pierced the gabbro, but in less 

 accessible localities we were told that the relations are reversed. 

 The granite at times seemed fairly to impregnate the gabbro with its 

 red orthoclase crystals and to half digest it, until the observer hardly 

 knew which rock name would apply. In another locality, Troll- 

 holmen, we saw contacts of gabbro on quartzite with similar absorp- 

 tion phenomena, leading at times to quartz-bearing gabbros. 



When the interpenetration of two deep-seated magmas becomes 

 very intimate and pressure phenomena or marked flowage later pro- 

 duce gneissoid structure, peculiar '* veined " or " injected " gneisses 

 may result. Finland also furnishes very instructive exhibitions of 

 these phenomena which were described to us by Professor Seder- 

 holm. In fact the members of the Congress who saw the exposures 

 and took part in the discussions based thereon, became deeply im- 

 pressed with the importance of always keeping in mind the possible 

 deep-seated conditions which have produced the phenomena and of 

 adjusting explanations in accordance with them. 



One extremely striking case of what is considered differentiation 

 was the object of a day's study on the island of Orno, just off the 

 coast, east of Stockholm. A central, coarsely crystalline mass of 

 diorite is surrounded by a border of finely but persistently banded, 

 differentiation products. The latter appear as light and dark bands, 

 respectively feldspathic (salic) and amphibolic, pyroxenic or 

 biotitic. 



The bands vary from a fraction of an inch to several inches in 

 width and with slight variation may run for hundreds of feet. 

 They are concentric with the diorite. They remind one of some 

 cases of persistent foliation in our old gneisses, such as the Ford- 



