Magncsian Limestone hi i lie Neighbourhood of Cork. 223 



square miles and squeezed the rocks of Cork and Kerr}- into 

 numerous folds. All this geological work would have had to 

 be accomplished before the close of the Permian period, for 

 time must of course be allowed for the newly-opened fissures 

 to be filled with their magnesian contents. As regards the 

 denudation, the most rapidly- working agencies with which we 

 are acquainted could not possibly have done this ; and we have 

 no particular reason to think that the monitors of the Califor- 

 nian gold-miners were anticipated and dwarfed by any 

 corresponding machinery guided by armies of lyabyrin- 

 thodonts. The view generally held b}' geologists regarding 

 the history of the Irish land-surface, assigns almost the entire 

 interval between the Carboniferous and the present time for 

 this denudation. Mr. Farrington's theor}^, how^ever, further 

 requires that the fissured limestone surface which formed the 

 bottom of the Permian lake, should have been preserved from 

 complete removal during the long Secondary and Tertiary 

 revolutions, with only a thin layer of '* soft Permian strata" to 

 protect it ; a layer which when the time came was cleared away 

 without difficulty by the glacial action which has been known 

 to spare many softer deposits. The acceptance of all this is 

 really impossible. 



The chemical part of the original theory of Harkness is cer- 

 tainly open to modification. It would seem that the alteration 

 of the Carboniferous limestone into dolomite was effected, not 

 by the magnesian salts in sea-water, but by magnesia held in 

 solution by carbonic or humus acids in the water which 

 penetrated downwards through the surface rocks. I am 

 inclined to think that in some cases a line of fault-rock 

 furnished a readier passage for the water percolating through 

 the limestone than its joints afforded, as the soft fissile layer 

 between the dolomite and the limestone which Mr. Farrington 

 has described looks very like a slickenside at times ; but this 

 is a point which is better left to those who can examine a great 

 development of the rock. I am quite convinced that nothing 

 is likely to be adduced regarding the Cork dolomites which 

 can seriously affect the main conclusion of Harkness, 

 that they are products of alteration. 



