G. H. WILLIAMS — OBSERVATIONS IN NORWAY. 551 



The next paper read is represented by the following abstract : 



GEOLOGICAL AND PETROGRAPHICAL OBSEKVATIONS IN SOUTHERN AND 



WESTERN NORWAY. 



BY GKORCiK U. WILLIAMS. 



\_Abstract.~\ 



The communication embodies the results of certain observations made by the author 

 during the summer of 1888 in southern and western Norway, under the guidance of 

 Professors Brogger and Reusch of Christiania, and in company with Professor Rosen- 

 busch of Heidelberg and Dr. A. C. Lawson of the Geological Survey of Canada. 



The points of special interest relate to the subject of metamorphism, which was 

 studied on a series of excursions in two regions exhibiting, in sharp contrast, the 

 effects (1) of the contact action of large eruptive masses upon nearly undisturbed 

 Silurian strata ; and (2) of intense dj'namic action in metamorphosing both igneous 

 and sedimentary material in a region of great orographic disturbance. 



Since the early travels of Von Buch and Naumann, the region about Christiania 

 has been classic as an example of the metamorphism produced at the contact of great 

 eruptive masses ; but the recent elaborate studies of Brogger show how much of value 

 there was to reward a detailed examination of this same Held. 



Large areas of post-Silurian syenite, granite and porphyry have broken through 

 the nearly horizontal Silurian beds, composed of thin, alternating layers of dark ar- 

 gillaceous, and light-colored calcareous material. The metamorphism is confined to 

 the immediate vicinity of the contact, and is progressive — i. c, proportional to the 

 nearness of the eruptive rock. The most intense action is shown upon fragments in- 

 cluded wholly within the syenite. 



In the region abost the Langesundfjord, southwest of Christiania, the conditions 

 and are about the same, except that the metamorphosing agent is here nepheline- 

 syenite, and particularly interesting on account of the great number of rare minerals 

 which it contains. Two points worthy to arrest attention are (1) the extent to which 

 the metamorphism of a sedimentary rock can be carried without destroying its fossils ; 

 and (2) the metamorphosing effects of eruptive masses upon other rocks themselves 

 eruptive. 



A specimen of limestone was exhibited from the immediate contact with the nephe- 

 line-syenite, near Brevig. It is completely changed by contact action, as is shown by 

 the microscope, to an aggregate of garnet and diopside, and yet remains of crirfoidal 

 columns are still plainly visible in it. 



The action of the syenitic rocks upon dikes of basic eruptives, present in the Silu- 

 rian beds before the intrusion of the more acid masses, is of interest, inasmuch as the 

 paramorphism of pyroxene to hornblende, which is now recognized as such a common 

 result of regional metamorphism, is here seen to have been accomplished by contact 

 metamorphism alone. 



A description was also given, illustrated by a diagram and specimens, of the Horter- 

 kollen granite mass, which has raised the overlying Silurian strata in the form of a 

 laccolite, though its base is not visible, and hence it is not definitely known whether 

 or not the sedimentary beds lie below as well as above the intrusive mass. This 

 mountain lies about twenty miles due west of Christiania, and is fortunately exposed 

 on its south side in a natural section from base to summit. The structure of the 



