﻿288 ME. A. M. FINLAYSON ON THE [May I9IO,. 



Limestone of Castletown. This association is also well seen around 

 Lough Corrib (Galway), where there is a group of lead-copper veins 

 occurring indifferently both in the Older Palaeozoic slates and in 

 the Carboniferous Limestone. It is not conceivable, in any of 

 these examples, that the veins in such adjacent districts can be 

 of different ages. Recorded instances of individual veins passing 

 from the Carboniferous Limestone into older rocks are not common, 

 as such veins generally become barren when they leave the lime- 

 stone and have not been explored further. The Pant-y-Buarth 

 vein, however, in the Carboniferous Limestone of Flintshire, was 

 traced into the Wenlock Shales on the west, 1 as was also the Old 

 Vein at Minera in Denbighshire. Shafts sunk on a copper-vein 

 at Great Orme's Head seem also to have followed the vein down 

 from Carboniferous Limestone into Ordovician or Silurian slates. 2 



In conclusion, it will be seen that all the available evidence 

 points in one direction, namely, that the vein-fissures are post- 

 Carboniferous and pre-Triassic, while the period of ore-deposition , 

 as indicated by the various examples given, also belongs to this 

 general epoch. This evidence, collected in all the typical vein- 

 districts throughout the British area, is considered to justify the 

 conclusion that all the deposits cited are of Hercynian age. 



It is evident that the ore-deposits here grouped together as 

 Hercynian are closely related to the various Hercynian deposits of 

 Western and Central Europe. Thus the fragments of the Variscan 

 Mountains contain the ore-deposits of the Harz and of Freiberg 

 and other important Saxon localities. The Armorican chain of 

 Britanny, Belgium, and Westphalia, and the Central Plateau of 

 France are marked by similar ore-deposits; while the Spanish 

 Meseta is another Hercynian fragment, richly metalliferous, espe- 

 cially in lead and zinc ores and in copper ores. Veins of tin, 

 copper, silver-lead, and zinc ores are characteristic of the Hercynian 

 metallogeny of Europe, 3 and the British ores here considered form 

 a portion of this great series. 



Before leaving the Hercynian Epoch, it should he pointed out 

 that there is a suggestion of relationship between the widespread 

 petrographic province of Caledonian granites and the similarly 

 widespread metallogenetic province of Hercynian ores. The rela- 

 tionship is not very intimate, but there is no other series of igneous 

 intrusions in the British area the distribution of which is in any 

 way comparable with the distribution of the Hercynian ore-deposits. 

 It is curious that, except in the Cornish area, the Hercynian 

 deposits are unaccompanied by genetically related igneous rocks. 

 There is, however, little doubt that the Hercynian ores have been 

 primarily derived from magmatic sources ; and, judging from the 

 foregoing considerations, it seems probable that the magmatie- 



1 A. Strahan, ' Geology of Flint, Mold, & Euthin ' Mem. Geol. Surv. 1890, 

 p. 188. 



2 A. C. Ramsay, ' Geology of North Wales ' Mem. Geol. Surv. 2nd ed. (1881) 

 p. 308. 



3 L. de Launay, C. R. Acad. Sci. Paris, vol. cxxx (1900) p. 745. 



