﻿286 mk. a. m. riNLAYsoN on the [May 19 10, 



this area, are considered, as pointed out above, to belong to the 

 older Caledonian Epoch. 



Turning to areas of Upper Palaeozoic rocks, still in the Northern 

 province, we have a second group of units, separated on geological 

 and geographical considerations. The Midland Valley of Scotland 

 is characterized by the silver-ore veins of Alva in Stirlingshire and 

 of Hilderston in Linlithgowshire, and by the zeolitic copper deposits 

 in the Carboniferous lavas of Renfrewshire and Dumbartonshire. 

 The Pennine Range, extending through the North of England down 

 to Derbyshire, is another unit, characterized by lead and zinc ores 

 throughout its whole extent, while fluorspar, barytes, and copper 

 ores are sporadically distributed. A third unit is made up of the 

 Carboniferous Limestone area of Flintshire and Denbighshire, also 

 yielding lead and zinc ores, but very little fluorspar or barytes. 

 The Northern province is completed by the central Carboniferous 

 plain of Ireland, containing scattered occurrences of lead, zinc, and 

 copper ores. 



The Eastern region is marked by occurrences of blende, galena, 

 and other ores in trifling quantities in the Keuper, Lias, and Lower 

 Oolite of several counties, and, more especially, by the bedded 

 cupriferous deposits of Alderley Edge and Mottram St. Andrews in 

 Cheshire. Similar deposits are also known in the Peckforton Hills 

 north of Whitchurch, at Grinshill near Shrewsbury, and in the 

 neighbourhood of West Felton, Oswestry. They are the British repre- 

 sentatives of the copper-bearing Triassic rocks of New Mexico and 

 Arizona, the Kupferschiefer of Mansfeld, and the lead-bearing sand- 

 stones (Bunter) of Commern and Mechernich. The ore-occurrences 

 of the Eastern district cannot be satisfactorily explained as due to 

 sedimentation. They represent the highest zone of Hercynian ore- 

 deposition in the British area, and indicate that the Hercynian 

 metallogenetic epoch extended well into the Mesozoic Era. The 

 absence of fissures to serve as trunk-channels and the impoverish- 

 ment, dilution, and dissipation of the solutions in this uppermost 

 zone, account for the paucity of ores. 



It is necessary to consider the evidence for placing all the ores 

 here enumerated in the Hercynian, more especially as many of 

 the areas are essentially Caledonian in their geological structure. 

 Evidence is to be obtained from a consideration both of the vein- 

 fissures and of the ores contained in them. 



With regard to the former, the vein-fissures of certain districts 

 are known to be post-Carboniferous or pre-Triassic, notably those 

 in the older rocks of the Lake District l and of North Wales. 2 In 

 the Isle of Man the fissures are later than the pre-Carboniferous 

 disturbances, 3 and are probably contemporaneous with those of the 



1 A. Harker, Quart. Journ. Geol. Soc. vol. li (1895) p. 126. 



3 A. C. Eam8av, 'Geology of North Wales' Mem. Geol. Sury. 2nd ed. 

 (1881) pp. 200-203, 264, 301 ; and A. Harker, 'The Bala Volcanic Series of 

 Caernarvonshire' Cambridge, 1889, p. 115. 



3 G. W. Lamplugh, ' Geology of the Isle of Man ' Mem. Geol. Surv. 1903, 

 p. 488. 



