﻿290 



MR. A. M. FINLAYSON ON THE 



[May 19 10, 



Pig. ] . — Section of Brow Vein, Leadhills ; 70-fathom 

 level, January 1909. 



C CTS C G 



[C = Calcite ; G- = Galena ; S = Crushed slate.] 



deeper levels of some 

 mines, where circu- 

 lating waters have 

 not re-arranged the 

 ores or formed later 

 ' pipes ' and ' flats.' 

 The primary ores, 

 galena and blende, 

 have been broken 

 up by movement 

 and re-cemented by 

 calcite or quartz. 



Mr. Gr. W. Lamp- 

 lugh has shown 

 that certain basaltic 

 dykes in the Isle of 

 Man, which are pro- 

 bably of Tertiary 

 age, lie alongside 

 lead-veins in such 



a manner that the 

 ores as now found 

 must have been deposited after, and probably in consequence of, 

 the intrusion of the dykes. 1 In these cases there is no evident 

 genetic relationship between the dykes and the ores, while the 



Fig. 2. — Section of Rampgill Vein, Nenthead, in the Great 

 Limestone ; main level east, December 1908. 



N. -^ hf M t ^. S. 



L ~~b C~ L C G L 



[L = Limestone ; B = Blende ; C = Calcite ; Gr = Galena.] 



larger and more productive veins of the Isle of Man are unrelated 

 to such dykes, and the veins where the phenomenon was observed 



1 ■ Geology of the Isle of Man' Mem. Geol. Surv. 1903, pp. 488-89. 



