Stratified Hocks near Killarney and Dnhlin. 173 



I shall next very shortly allude to another point brought 

 forward by Mr. Hamilton in his paper. In speaking of the 

 district coloured old red sandstone on my large geological 

 map which occupies extensive tracts in the counties of Water« 

 ford and Cork, he observes, " As to classification, it appears 

 to me that Mr. Griffith has thrown together two rocks which 

 are very distinct, namely, 1st, The old red sandstone and its 

 conglomerates ; 2ndly, Compact arenaceous rocks, agreeing in 

 geological position with the upper part of the Devonian series, 

 as described by Professor Sedgwick and Mr. Murchison." 



It appears to me that Mr. Hamilton is mistaken in separa- 

 ting the old red sandstone from the Devonian system, as Pro- 

 fessor Sedgwick and Mr. Murchison include the whole series 

 under the general term Devonian : consequently, whether we 

 apply the term Devonian, or old red sandstone, to the system, 

 no advantage could be derived from its arbitrary subdivision. 



I freely admit that doubts may be entertained as to whether 

 the yellow sandstone and carboniferous slate, considered by 

 me to belong to the lowest portion of the carboniferous sy- 

 stem, should not be placed at the top of the old red sand- 

 stone or Devonian system. This however is not a question 

 of position, but of fossils ; and as far as my present informa- 

 tion extends, I still feel inclined to adhere to my original view, 

 founded on the fact, that in ascending in the old red sand- 

 stone series the first alteration observed is a change from 

 7'ed and yellowish green clay slate, to yellow quartzose sand- 

 stone passing into light gray, which contains in abundance 

 the peculiar variety of calamite already mentioned. Below 

 this sandstone no fossil remains have been discovered ; above 

 it they occur in abundance, and the upper beds which alter- 

 nate with gray clay slate and limestone contain fossils which 

 undoubtedly belong to the carboniferous limestone, though 

 doubts may be entertained respecting a kw which occur to- 

 wards the bottom of the series. 



Should it appear on a more careful and extended examina- 

 tion that some of the fossils of these lower beds are similar to 

 those which occur in the upper part of the Devonian system, 

 difficulties will still arise as to where in a graduating series 

 the line should be drawn separating the Devonian from the 

 carboniferous system ; and as far as Ireland is concerned, I 

 think I have adopted that which appears to be least liable to 

 objection ; but even on this point 1 am open to conviction. 



In the mean time the fact to dwell upon is, that the mineral 

 succession which I have pointed out beneath the carboniferous 

 limestone of Ireland, is similar to that described in North De- 

 von by Professor Sedgwick and Mr. Murchison. 



In the conclusion of his paper Mr. Hamilton observes, 



