﻿Vol. 66.] METALLOGE^Y OF THE BEITISft ISLES. 285 



Hercynian Epoch. — This epoch is by far the most important 

 in the area, since it is believed to embrace all the ore-deposits not 

 included in the two preceding divisions. The corresponding metallo- 

 genetic province may be subdivided into three distinct subprovinces 

 or regions, based on differences in geological structure. These 

 groups are a Southern or Armorican, embracing the fragments of 

 the old Armorican Mountains in Southern Ireland and the South- 

 West of England; a Northern, including all the other areas of 

 Palaeozoic rocks in England and Wales, Southern Scotland, and most 

 of Ireland ; and an Eastern region, embracing the Mesozoic area of 

 Centra] and South-Eastern England. It is, of course, not intended 

 to suggest that there is any essential difference in the tectonics 

 of these three areas. The subdivisions, which are tabulated in the 

 classification set out on a later page, are made for convenience of 

 description, and in order to emphasize the geographical and 

 geological relations of the different groups of ore-deposits. 



The Southern district, both in respect of its geological structure 

 and of its ore-deposits, is marked off on the whole from the districts 

 to the north of it. The ores comprise the abundant copper, lead, 

 and zinc veins in the counties of Kerry, Cork, and Waterford, the 

 deposits in the Mendip and Quantock Hills of Somerset, and the 

 tin-copper ores of Cornwall and Devon, with the associated lead 

 and zinc ores. The chief features of this Armorican region are the 

 marked local development of tin, and the general abundance of 

 copper. Like the geological structure of the region in which they 

 occur, the ore-deposits have Continental affinities. It is a peculiar 

 circumstance that the highly disturbed district of Pembrokeshire, 

 which in Palaeozoic times was more than once a theatre of igneous 

 activity, and was involved in the Armorican movements, should be 

 barren of ore-deposits. 



The Northern region may be subdivided on a basis of geological 

 and geographical continuity between its various fragments. Thus, 

 taking first the areas of Lower Palaeozoic rocks, the Southern 

 Uplands, the Lake District, the Isle of Man, and North-Eastern 

 Ireland constitute an ore-bearing unit. This area is characterized 

 in general by veins of lead and zinc ores, with copper in places, 

 some antimony, and traces of cobalt ore ; while gold occurs in the 

 Southern Uplands, and has been recorded also from the Lake District. 

 It will be observed that the Caledonian granites are abundantly 

 developed in all these districts. A second unit comprises the 

 North-West and West of Ireland, chiefly the counties of Donegal, 

 Mayo, and Gal way. The ores here are similarly lead, zinc, and 

 copper; while the Caledonian granite is again prominent in Donegal 

 and Galway. A third unit, well-defined, embraces Northern and 

 Central Wales, Anglesey, and the South-East of Ireland. This area 

 differs somewhat from the other two : while lead and zinc ores 

 are still abundant, copper is much more prominent, especially in 

 Carnarvonshire, and there is also the well-marked gold-belt of 

 Merionethshire. Einally, antimony, nickel, and cobalt are rare or 

 absent. A marked feature is the localization of these copper and 

 gold districts. The pyritic masses of Wicklow and Anglesey, in 



