124 Mr. E. T. Hardman, 



is certain therefore that these lodes, as well as the copper lodes 

 of the other parts of Cork as well as Kerry, are younger than the 

 Carboniferous period, and may be therefore about the same age 

 as those of Cornwall. It is, of course, impossible to determine at 

 what period past the Carboniferous they have been deposited, since 

 there are no newer strata in this part of Ireland ; but however 

 this may be, we may suppose that the original fissures were most 

 likely opened during the disturbances which produced the 

 flexures of the Old Red Sandstone in the south-west of Ireland. 



Deposition of the Barytes and associated Minerals. — Barytes 

 being one of the most insoluble substances known, it is unlikely 

 that it could have been deposited from solution in cold water ; on 

 the other hand it is so very infusible that the heat necessary to 

 reduce it to a plastic condition would be more than sufficient to 

 melt the surrounding rocks. Its deposition is therefore to be 

 ascribed with most probability to the action of thermal springs, 

 the waters of which were forced upwards into these fissures, while 

 the strata at present exposed were still buried under a great mass 

 of superincumbent rocks. The waters at first warm enough to 

 hold small quantities of such difficultly soluble minerals , in 

 solution would, as it came nearer the surface, become somewhat 

 cooler, and these minerals would be then deposited along the sides 

 ot the fissure. This point, which is insisted on by Delesse, is 

 demurred to by Bischof, who considers that the waters of ascend- 

 ing hot springs cannot produce these deposits, but it is evident he 

 left out of consideration the cooling of the water as it rose. 



Source of the Sulphate of Barytes. — This is to be sought for 

 either in the immediately outlying or surrounding rocks, or in 

 masses of rock at some distance, from which some compound 

 of barium may be carried down into springs. Carbonate of barium 

 is by no means an uncommon mineral, and barium in some form 

 is of common occurrence in minute proportion in limestone. Sili- 

 cate of barium is also found occasionally in igneous rocks, and 

 might, therefore, also occur in parts of the Old Ked Sandstone 

 which are derived from the debris of such rocks*. Those com- 



* The very small quantity of Barium compounds disseminated through rocks, is of 

 little moment in this consideration. As Bischof well remarks, the minimum quantities 

 in rocks may become the maximum quantities in lodes. 



