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 
of 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- 
eate of barium is also found occasionally in igneous rocks, and 
might, therefore, also occur in parts of the Old Red 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. 
