124 Rev. J. Clifton Ward — Geology of the Lake District. 



Graptolites below a certain horizon, such an horizon not necessarily 

 indicating any long break. 



Among rocks in which there so frequently occur great thicknesses 

 of wholly unfossiliferous beds, the mere absence of a particular fossil 

 or group of fossils cannot go for much. Thus, over large tracts of 

 the Lingula Flags in Wales, no Lingulas or other fossils occur, while 

 in some spots they may be plentiful enough. Hence, although no 

 Lingula Davisii has been found in the lower sandy series of White- 

 side and Grasmoor, this cannot be used as evidence against the 

 Lingula Flag age of these beds if that be supported on general 

 physical grounds. 



Summary of Evidence. — The Physical evidence inclines one to 

 believe that the Skiddaw Slates include the Arenig Slates, the Arenig 

 Grit, the Tremadoc Slates, and the Lingula Flags. The Paleeon- 

 tological evidence, based on no complete assemblage of life, and 

 having no fossiliferous formations to which to refer above and below, 

 suggests an Arenig age for the whole series on one score, and a 

 possible Tremadoc age for portions of it upon another score. Hence, 

 may we not conclude it to be at all events very possible that in 

 Cumbria we have the equivalents of the Welsh rocks down to the 

 Lingula Flags? 



If we consider the Lingula Flags and Tremadoc Slates as 

 Cambrian, all that portion of the small Sketch-map denoted by 

 broken vertical lines will represent the Cambrian, and that above 

 the Grit the Silurian. 



Explanation of SKETCH-MAP, Plate II. (Geol. Mag. Feb. 1879, p. 49.) 



Fig. 1. Diagrammatic Section, from N. to S., to show general structure of District. 



Fig. 2. Diagram to show plateau of marine denudation, at the close of the Old Eed 

 period. The pattern used to denote the Upper Silurians is not meant to 

 indicate that the strata are vertical, though they are generally highly inclined. 



Sketch-map of the Geology of the Lake District. The lines along which the 



Horizontal Sections on p. 54 are drawn are indicated in the Sketch-map. 



APPENDIX. 



List of Papers, by the Author, on Lake District Geology, to be 

 referred to in connexion with this paper. 



Notes on the Microscopic Structure of some Ancient and Modern Volcanic Eocks. 

 Quart. Journ. Geol. Soc. vol. xxxi. p. 388. 



On the Granitic, Granitoid, and associated Metamorphic Eocks of the Lake 

 District. Ibid. vol. xxxi. p. 568, and vol. xxxii. p. 1. 



Part I. — On the Liquid Cavities in the Quartz-bearing Eocks of the Lake 



District. 

 Part II. — On the Eskdale and Shap Granites, with their associated Metamor- 

 phic Eocks. 

 Part III. — On the Skiddaw Granite, and its associated Metamorphic Eocks. 

 Part IV. — On the Quartz-Felsite, Syenitic, and associated Metamorphic 



Eocks. 

 Part V.— General Summary. 

 The Geology of the Northern Part of the English Lake District. Memoirs of the 

 Geological Survey. Longmans & Co., and E. Stanford. 



Notes on the Occurrence of Chlorite among the Lower Silurian Volcanic Eocks of 

 the Lake District. Mineralogical Mag. No. 4. 



On the Lower Silurian Lavas of Eycott Hill, Cumberland. Monthly Microscop. 

 Journ. 1877, p. 239. 



