428 Reviews — The Geology of Northern Norway. 



specimens obtained from various sources were also examined 

 petrographically, and the results obtained are here discussed from the 

 theoretical and practical points of view. 



The following are the chief minei'als observed: wollastonite, quartz, 

 tridymite, melilite, augite, sillimanite, corundum, biotite, and 

 magnetite, as well as a mineral having the composition 3Ca0.2Si0 2 , 

 not known to occur in nature. In the general body of the glass the 

 chief minerals found were wollastonite and tridymite, and their 

 presence is of much interest as indicating that owing to the presence 

 of other substances acting as fluxes the crystallization took place 

 below the inversion-points of pseudowollastonite to wollastonite and 

 of cristobalite to tridymite. Wollastonite was very abundant in the 

 specimens and showed a strong tendency to spherulitic aggregation, 

 a feature noted also in other cases of a similar nature. Augite 

 and quartz were found only in thin strings of glass injected 

 into cracks in the bricks or at the junctions of glass and brick. The 

 augite is a variety containing a good deal of manganese. 



Under certain conditions wollastonite, augite, tridymite, and quartz, 

 can all crystallize out from the same melt, while felspar, magnetite, 

 and biotite are formed by the corrosive action of glass on brick. 

 Wollastonite, melilite, augite, and the 3Ca0.2Si0 2 compound were 

 produced in partly assimilated limestone fragments enclosed in molten 

 glass. The action of molten glass on aluminous materials used to 

 contain it in the form of glass-house pots, furnace linings, and crown 

 bricks leads to the formation of sillimanite and corundum in 

 considerable quantities, some specimens examined containing very 

 well developed crystals of both mineral. 



It is impossible here to detail all the results following from this 

 careful examination of the material available and the theoretical 

 deductions to be drawn from it : the paper is of great interest and 

 should be studied carefully by all penologists interested in the genesis 

 of the minerals of the igneous and metamorphic rocks. 



VIII. — The Geology of Northern Noravay. 

 Suliteliiatrakten. By Gr. Holmsen. Norges Geol. Undersok. 



Aarbok for 1917, 'ni, pp. 44, and 2 plates (with English 



Summary). 

 Fjeldstroket Fauske-Junkerdalen. By J. Bekstad. Ibid, iv, 



pp. 66, with 7 plates and a coloured map (with English 



Summary). 

 TIIHESE two memoirs give an account of the geology of the tract 

 _L of country between the Saltenfjord and the Swedish frontier, 

 which includes the well-known copper-mines of Sulitelma, now 

 being extensively worked. It is an area of high mountains and 

 plateaux, some points rising to 6,000 feet above the sea, and 

 supporting several important glaciers. The region consists of 

 gneisses, crystalline schists, amphibolites, and marbles, penetrated 

 by igneous rocks of Caledonian age, ranging from serpentine to 

 granite, the latter occupying the largest area. Some interesting 

 examples of sheared and folded conglomerates are described and 



