4o6 SCIENCE PROGRESS 



Scandinavia. In 1888 he redescribed the geology of Areskutan,^ 

 and identified the schists and gneisses of the summit of the 

 mountain as pre-Silurian rocks, pushed from the west over 

 the lower but 3'ounger Palaeozoic sediments. This view is 

 represented in fig. 4 from Tornebohm's memoir of 1896. 



In 1891 Tornebohm explained other cases of the apparent 

 interstratification of slates and quartzites with gneisses as 

 due to inversion b}^ folding. Thus on the northern foot of 

 the Jotun-Fjall in Norway, on the southern shores of Lake 

 Vage, the apparent sequence consists of the following beds, 

 all of which are dipping southwards: (5) upper gneiss, (4) 

 upper quartzite, (3) clay slate, (2) lower quartzite, (i) lower 

 gneiss. Tornebohm explained this arrangement as due to an 

 isoclinal, by which the quartzite and gneiss are repeated on 



S = Silurian. m = Meraker Schists. a = Are Schists. 



Q = Quartzite. r = Roros Schists. T.P. = Thrust Plane. 



Fig. 4. — Section through Areskutan after Tornebohm, 1896, showing the Are schists 



as pre-Silurian. 



both sides of the slates. ^ According to this interpretation there 

 are only three beds, and the gneiss is the oldest. 



This conclusion was, however, rejected by Bjorlykke, who in 

 1894 accepted the fact that much of the so-called Mountain 

 Quartzite {Hoifjcldskvartseri) of the Norwegian Fells w^as a 

 gneiss and not a quartzite ; and he claimed that this gneiss 

 was of post-Ordovician age, and that the crystalline rock had 

 been originally deposited unconformably on the unaltered, 

 older Ordovician beds.^ 



In 1905 Bjorlykke issued as No. 39 of the Norgcs Geologiska 

 Undcrsogelse a work on the mountain structure of Central 

 Norway, in which he maintains that the upper sparagmite 

 group is of Devonian age, and that, for that area, " the theory 

 of overthrusting must be abandoned." For the geology of 



' A. E. Tornebohm, " Om fjallproblemet," Geol. For. Fork. vol. x. (188S), pp. 

 328-36. 



- A. E. Tornebohm, " Om hogfjallsqvartsiten," Geol. For. Fork. vol. xiii.(i89i), 

 p. 41- 



' K. O. Bjorlykke, " Hoifjeldskvartsens nordostligste udbredelse," Nors^es Geo.. 

 Undersbg. No. 14 ; Aarbog for 1892 eg 1893 (1894) pp. 64, T^i-: 74- 



