44-4 Mr. C. W. Hamilton on the Older Rocks in the 



abella. Two years previously I had shown him my reasons for 

 believing that the roofing slates there quarried were newer 

 than the old red sandstone, and in the map published this 

 year, he has adopted the correction. The section implied in 

 the present map differs totally from that which I made in 

 1836, from Tralee to Kenmare (Journal of the Dublin Geol. 

 Soc. vol. i. pt. 4.). He has represented the old red sandstone 

 as merely a cap upon Magillicuddy's Reeks, (PI. I. f. 2.) and 

 assigned to the Cambrian epoch the mountains between them 

 and Kenmare, which I represented as intermediate between 

 the old red sandstone and mountain limestone. 



Captain Portlock, in his two addresses from the chair of the 

 Dublin Geological Society, has questioned even the existence 

 of the old red sandstone upon Caranthuel. 



In the " Outline of the Geology of Ireland," appended to 

 the Second Report of the Railway Commissioners in 1838, 

 Mr. Griffith describes the " mountain tract which comprises 

 the whole of the county of Waterford, and large portions of 

 the counties of Cork and Kerry, as containing ' two varieties 

 o^ transition slate '^ tlie second or newer slate usually rests 

 unconformably on the older; the lower portion of its strata 

 consists of alternating beds of brownish red quartzose conglo- 

 merate and coarse red slate ; these strata are succeeded by 

 alternations of red and grey quartz rock, red quartzose slate, 

 and clay slate ; the grains becoming finer as the beds accu- 

 mulate, and recede further from the conglomerate, till at 

 length the upper beds produce varieties of purple, brownish 

 red and reddish grey clay slate, which are quarried for roofing 

 slate, particularly in the valley of the Blackwater, as at Lis- 

 more." He then describes the old red sandstone, yellow sand- 

 stone, and mountain limestone, as ne^weraxiA superior to these 

 slates. 



In the map published this year, he has included under the 

 head of old red sandstone most of these slates, and cites as 

 an example, the slates alluded to in the report as quarried 

 near Lismore ; but as in other places there appeared to be 

 so wide a difference between his map and my sections, I 

 again visited that part of the country this autumn, and although 

 the want of a correct geographical map and the lateness of the 

 season pi'evented me from working accurately in estimating 

 thicknesses, &c., I saw enough to satisfy me that my own 

 views in respect to the order of superposition had been 

 correct. 



As to classification, it appears to me that Mr. Griffith has 

 thrown together two rocks which are very distinct and easy of 

 recognition, namely ; 



