274 NEOZOIC TIME. [CHAP. XIII. 



tinctly marked along the flanks of the more abruptly rising 

 hills on each side of the valleys." ] 



This Limestone Drift seems to be connected with a period 

 of submergence, for it sweeps up to heights of 1,200 and 

 1,300 feet, and at these heights there are marine deposits 

 like those of Wales, containing shells which do not indicate 

 any great intensity of cold, but include some species which 

 have a southern range, such as Venus casina and V. striatula. 



In the north-east of Ireland and along the borders of 

 the Irish Sea deposits occur which are in part similar to 

 the low-level marine Drifts of western England, but the 

 notion that these and the older Boulder-clay on which they 

 rest constitute three distinct stages, namely, a set of sands 

 and gravels between two sheets of Boulder-clay, appears to 

 have been founded on a double misconception. In the 

 first place, such a general threefold division does not exist 

 in Lancashire (see p. 268) ; in the second, and assuming 

 that it does so appear in Ireland, it does not follow that 

 the lowest clay there is the same as the lowest Boulder- 

 clay in Lancashire ; that it is, in fact, a very different clay 

 we have the following testimony by Mr. Mellard Reade : 2 

 " What Hull calls the Lower Boulder-clay in Ireland is a 

 deposit of an entirely different nature to that of Lancashire, 

 which is undoubtedly marine, containing rounded boulders 

 of travelled stones as well as shell fragments. Whereas 

 the Irish Lower Boulder-clay is distinguished by the local 

 character of the stones it contains, the absence of shells or 

 shell-fragments, and the general appearance (? resemblance) 

 it bears to moraine matter." 



Neither do the facts recorded by Messrs. Hull, J. G-eikie, 

 and Hardman, 3 afford sufficient ground for labelling any 



1 <: Manual of Geology," second edition, p. 676. 



2 " Notes on the Geology of Ireland,'' Proc. Liverp. Geol. Soc.. 1879. 



3 See " The Great Ice Age," second edition, p. 595, for details and 

 references. 



