Feb. 1897.] - 29 



THE FORMER ABUNDANCE OF GRANITE BOULDERS 

 IN THE S.E. NEIGHBOURHOOD OF DUBININ. 



BY KeV. MAXWE^I,!, H. CI^OSE), M.A., F.G.S. 



(Read before the Dublin Naturalists' Field Club, Sth December, 1896.) 



The presence and distribution of boulders in a particular 

 district is generally very interesting, and indeed often 

 geologically significant and important, in various ways. But 

 unfortunately in such a neighbourhood as that of Dublin they 

 are specially liable to be removed for various reasons. When 

 they interfere seriously with the cultivation of the land we 

 cannot blame the farmers for getting rid of them, and when a 

 great deal of building material is required we cannot wonder 

 at the contractors breaking them up and carrying them off 

 from rough wild uncultivable places where the farmers would 

 let them remain. But the extensive removal of them may 

 hereafter cause perplexity to geologists, and even lead them 

 into error, if they should be not sufficiently aware of the 

 former state of things. These remarks apply very specially to 

 the southeast neighbourhood of Dublin, where there has 

 been such extensive destruction of boulders. When the Geo- 

 logical Survey were at work in this district they had not 

 begun to pay as much attention to surface geology as they 

 did afterwards, so that the Explanations of Sheet 112 say 

 nothing on the limited subject of this communication ; it 

 seems, then, desirable that the Dublin Field Club should 

 record the facts with which we are now concerned. 



The granite boulders of this region do not generally belong 

 to the bonlder-clay. They usually lie on it, though they are 

 often partially buried in the drift. They are generally of 

 later date than the detrital deposits on which they rest, and 

 have sometimes moved in a direction contrary to that in which 

 the latter have been carried. This can be seen near the west- 

 ward edge of the granite district, as, for instance, in the lower 

 part of Glennasmole, where the deep deposit of limestone 

 materials has come from the plain country on the west, and 

 the overlying granite boulders from the eastward. 



The extensive disappearance of these boulders from the 

 district now in question has doubtless been observed by 



A 



