30 Mr. Weaver on the Geological Relations of the South of Ireland. 



The outcrop of this bed at the surface appears in the form of iron ochre, which in the western 

 part contains some intermingled portions of galena. 



(45.) The earliest working of the Ross Island mine, is ascribed to the times of the Danish in- 

 roads ; and the shallow parts above the level of the lake were evidently wrought by fire, being 

 composed of chambers of a rudely vaulted form. The works have been resumed at various periods; 

 one of the latest was in the year 1804, from which time the operations were continued until 1810. 

 In this interval 3220 tons of ore were raised, the sale of which amounted to 69,487^., being on an 

 average about 21^. per ton ; and the standard price of copper during those years having averaged 

 135^. per ton, the ores appear to have yielded 17^ per cent, of copper. 



In the year 1825 my attention was drawn to this mine, then filled with water, the level of which 

 corresponded with that of the lake. The mine had been represented by some as a metalliferous 

 bed, dipping to the south at an angle of 16° from the horizon, yet partially connected with irregular 

 contemporaneous veins ; while by others it was considered as a rake vein. In reference to what 

 follows, the annexed plan and section of Ross Island mine will be found serviceable. They repre- 

 sent the state in which the mine was left in the summer of 1829. 



Plan of Ross Island Mine veith the Embankment. 



Deep level. 



Section of Ross Island Mine and Embankment from S. to N. on the line A — B. 



1 ^ 1 ?> 1 ?; 



./ 



V 



o &: 



Low Level of Lak< 



