466 E. HAEKNESS AND H. A. NICHOLSON ON THE STEATA BETWEEN 



At Shap Wells, close to the medicinal spring, occurs a singular 

 band of Coniston Limestone, to which we shall have occasion to 

 refer again. 



The band in question is a calcareous breccia composed of innu- 

 merable fragments of various rocks, mostly under a quarter or half 

 an inch in diameter, imbedded in a calcareous matrix. Thin sections 

 of this rock are very difficult to prepare, owing to the large number 

 of angular fragments of quartz which they contain ; in addition to 

 which there are numerous fragments of limestone, felsjmthic ash, and 

 perhaps traps, the cementing matter of the whole being a granular 

 ►limestone apparently devoid of fossils. That this breccia is more or 

 less altered by the near vicinity of the Shap granite cannot be 

 doubted, the more so as the graptolitic mudstones are seen in an 

 unequivocal form about 200 yards to the south of the breccia, with 

 numerous graptolites, but so highly indurated as to have become 

 almost flinty in their fracture. In connexion with this we may 

 briefly refer to the microscopic characters of the more highly meta- 

 morphosed Coniston Limestone, about a quarter of a mile from the 

 mineral spring, near the top of the BJea Beck. Here the Coniston 

 Limestone is penetrated and apparently overlain by a mass of fel- 

 stone, doubtless emanating from the granite of Wastdale Crag. In 

 the immediate vicinity of this intrusive mass, the limestone is con- 

 verted into an olive-green splintery rock, which shows, in micro- 

 scopic sections, particles of iron pyrites and disseminated specks of a 

 dark green mineral (hornblende?), together with a few traces of 

 minute fossils. At a distance of a few yards from the felstone this 

 limestone presents itself as a dark grey crystallized rock, which is 

 shown by thin sections to be completely granular, with hardly any 

 indications of fossils. 



About two miles west from Shap Wells, at a short distance to the 

 south-west of the farm-house of "Wastdale Head, the Coniston Lime- 

 stone exhibits itself in a very highly metamorphosed condition. 

 Here, in the course of a small stream flowing from the north, a 

 small patch of the limestone occurs, having a white colour and a 

 crystalline structure. A few feet to the north of this patch a small 

 exposure of rock is seen, having a gneissic character, the particles of 

 which are very crystalline. This gneiss is very nearly in contact 

 with the south-west portion of the Wastdale-Crag granite. It is 

 probably either metamorphosed shales of the Coniston Limestone, or 

 of the representatives of the Dufton Shales. 



The white crystalline limestone has peculiar features. It has a 

 fine scaly structure, with a pearly lustre, and resembles fine-grained 

 Schiefer spar. It contains within it Idocrase ; and in the upper 

 portion, where it has been subjected to the action of the water of 

 the stream, the idocrase almost remains alone, the carbonate of lime 

 having been removed*. 



* Idocrase or Vesuvian, as the latter name implies, is a rather common 

 mineral in connexion with the volcanic products of Vesuvius, being often found 

 in a crystalline limestone ejected from this volcano. It also occurs in the 

 metamorphic Lower Silurian Limestone in Glen Laion, Aberdeenshire, and 



