THE SHAP GRANITE AND ASSOCIATED ROCKS. 317 



granite of Eker and Sandsviir, near Christiania *. English geolo- 

 gists who have read the masterly memoirs of Lessen, Brogger, and 

 Laug will be interested to learn that many of the phenomena 

 described by the Continental petrologists may be studied in our own 

 country. The metamorphism near the Shap Fell granite is as com- 

 plete as any described in similar strata, the rocks being entirely re- 

 constituted with expulsion of the whole of the carbonic acid. 



D. The Silurian Rocks. 



Owing to a strike-fault, which has already been alluded to, the 

 lowest members of the Silurian are not seen in our district. The 

 next set of rocks to be noticed is the Lower Coniston Elags or 

 Brathay Elags, which are well exposed, and can be traced to within 

 about 350 yards of the granite. There is little doubt that these 

 strata are in contact with the intrusive rock along its southern 

 boundary, but this junction and the inner ring of the aureole of 

 metamorphism are concealed by superficial accumulations. For 

 this reason, and in view of the numerous descriptions of meta- 

 morphosed argillaceous rocks already given by various writers, 

 it will not be necessary to treat the rocks in question at great 

 length. We shall confine ourselves chiefly to following the stages 

 of alteration exhibited by the rocks exposed along the banks of 

 Wasdalc Beck. As the line thus traversed coincides very closely 

 with the strike of the beds, we need not expect to find any varia- 

 tions other than those due to varying degrees of metamorphism. 



The exposure nearest to the Hotel is about 1400 yards from 

 the granite outcrop as laid down on the map, and here the meta- 

 morphism is very slight. It consists in a certain hardening of 

 the rocks and a partial loss of the fissile character, though both 

 bedding and cleavage are still easily made out. The flags here 

 have a dull black colour, due no doubt to organic material, and they 

 contain recognizable graptolites. The specific gravity is 2-7645. 

 A slice [863] from this locality shows abundance of carbonaceous 

 matter, mainly arranged along the direction of lamination, which 

 is crossed at an acute angle by cleavage. There are also minute 

 angular grains of quartz. These constituents are embedded in a 

 mass of finely-divided dusty matter, such as might arise from 

 decomposed felspathic fragments, with a certain amount of quartz- 

 cement. The specimen does not differ materially from the Brathay 

 Flags of Stockdale [1284]. 



Following the rocks up the beck, we observe that from dark they 

 become yellowish-grey in colour, but with countless little black 

 spots which take on the lustre of mica. The spots are seen as far 

 as the flags can be traced, that is, within about 350 yards of the 

 granite. A specimen here has a specific gravity of 2*732, which is 

 lower than that of the less altered rock. 



A microscopic examination of the specimens shows that the outer 



* Brogger, ' Die silurischen Etagen II. und III. im Kristianiagebiet ' (1882) ; 

 863 also Lang, Nyt Mag. Naturvidensk. vol. xxx. pp. 335 et seqq. 



