13^ The Irish Na he ra list. 



deposited in its present position, and that the latter is not the 

 result of the tilting-up of strata originally horizontal. 



In addition to denudation, it seems as if the strata had been 

 subjected to a degree of heat sufiQcient to weld them together 

 without such fusion as would completely destroy the previous 

 arrangement of their parts. The presence of large crystals of 

 iron pyrites in the magnesia-stone seems to favour this view, 

 as also its crystalline structure. Prof. M. M. Hartog, of 

 Queen's College, Cork, who has kindly examined for me a 

 mounted section of the minerals in juxta-position, says the 

 dolomite is in the form of saccharine marble, while the lime- 

 stone is not nearly so much metamorphosed. 



To ascertain the character of the organic remains will, no 

 doubt, help much in elucidating the question of the common 

 or distinct origin of these rocks. This is, however, rendered 

 somewhat difficult by the consideration just alluded to, and it 

 is only rarely that distinct fossils are obtained from the dolo- 

 mite-bearing limestone of the district. In only one or two 

 cases have I found signs of life in the dolomite — viz., some 

 small crinoids, and some tiny shells in a few weathered speci- 

 mens. More distinct and larger fossils may be found in the 

 pure limestone, but not to anything like the extent that 

 obtains in other parts, the I^ittle Island quarries for instance. 

 Judging from these limited materials, the palaeontological 

 evidence is not adverse to my theory, but it can hardly be of 

 much value until a closer examination has been made. 



The theory of the origin of these deposits to which the fore- 

 going among other facts have led me, may be briefly stated as 

 follows : — After the deposition of the Old Red Sandstone, the 

 Carboniferous limestone, and the Coal Measures, these strata 

 were distorted by terrestrial disturbance, and thrown into the 

 succession of parallel hills and valleys which we find now 

 forming an important feature of our southern Irish scenery. 

 A period of denudation then set in which cleared away nearly 

 all the Coal-MeasurCvS, carried off the limestone from the hill- 

 tops, and exposed the Old Red Sandstone over most of the 

 countryside. 



As the result of upheaval, long cracks and fissures may have 

 been formed in the limestone, in a direction parallel to the 

 lines of hills, i.e., east and west, or rapid streams running down 

 the valleys, and possibly charged with solvents, may have 



