318 Revieii's — Postlethicaite' s Mining in the Lake District. 



sources of mineral wealth, the knowledge of which is of great antiquity, 

 some of the mines having been worked by the Eomans during their 

 occupation of this country, and probably by the Britons before them. 



Both the physical features and the mineral contents of the rocks 

 are due to the geological character of the district, which consists 

 chiefly of the Skiddaw slates, with the associated granite and meta- 

 morphic schists, and the overlying green slates and porphyries 

 (Borrowdale series). These rocks, elevated, indurated, contorted and 

 faulted, have subsequently and for long ages been weathered and 

 disintegrated by various meteoric agencies acting on the hard and 

 soft strata, — thus producing the present irregular outline of cliff, 

 ravine and valley, due primarily and partly to a former glacial 

 period which has left its traces in the scored rocks, rounded hum- 

 mocks, and thick accumulations of moraine materials in the present 

 valleys, and which, as well as the other geological features, have 

 been so ably described by Mr. C. Ward in his memoir lately pub- 

 lished and noticed (Geol. Mag. 1877, p. 280). 



On the other hand, the mineral veins and lodes are the result of 

 those mysterious processes, deeply seated perhaps, by which the con- 

 taining fissures became filled with various kinds of metallic matter, 

 with which the Lake District abounds, for no less than 86 species of 

 minerals have been noticed, of which 46 are metallic, and 40 non- 

 metallic ; some of them being most rare and beautiful forms. The 

 principal mines from which these minerals have been obtained are 

 arranged by the author in the order of the strata in which they 

 occur, commencing with those in the Skiddaw slates, which are 

 numerous and extensive, the veins being generally large and well 

 mineralized, but sometimes irregular in the deposits of ore. 



The mines in the green slates and porphyries are not so numerous 

 as those in the Skiddaw slates, but some of them are much more 

 productive. The most remarkable of these mines is the plumbago 

 mine, which is well known to be unequalled for the purity of the 

 graphite obtained from it ; the containing vein or dyke is a species 

 of hard trappean or diabasic rock of a peculiar nature, the deposits 

 of plumbago occur in sops or pipes of various sizes, and not in veins. 

 The Coniston copper mine and the Green side lead mine are in the 

 same formation, the latter being one of the most valuable mines in 

 the North of England. 



The mining field of Caldbeck Fells is in the porphyritic syenite, 

 in which seven distinct mines have been opened. Of these the most 

 important and productive is the Eoughtengill, both as regards the 

 quantity and variety of its ores and minerals. Besides the metallic 

 mines, the Caldbeck district includes the north-western portion of 

 the West Cumberland coal-field, in which a small seam of coal was 

 wrought as early as 1790. 



The work is illustrated by a map of the mining field of the Lake 

 District, with section and plans of the principal mines, together with 

 a synopsis of the State papers relating to the mines and smelting 

 works near Keswick. The author, practically acquainted with the 

 mining district, and evidently interested in the mineral development 



