( 'J-^ ) 



MINOR rERIODIClTY IN GLACIAL KETKEAT. 

 By W. B. AVRIGHT. 



[communicated by permission of the director of the GEOLOaiCAL SURVEY OF IRELAND.] 



Plate XV. 



[Rea<l Jaxuahy 12. rciblislied May I'.l, 1920.] 



Those who are well acquainted with the Highlands of Scotland will have 

 recognized that, generally speaking, the moraines of that mountain district 

 do not assume any pronounced linear arrangement. In most cases there is 

 nothing but a wild profusion of irregularly scattered mounds. The areas 

 which have come within the scope of my own observation show this condition 

 of things as the normal type of lowland and valley-bottoin topography. 

 Here and there, it is true, a rude linear arrangement can be detected by a 

 careful observer, but it seldom has any persistence, and is mostly confined 

 to the mountain slopes. There must of course be cases of well-marked 

 linear moraines here and there in the Scottish mountains — indeed, photographs 

 have been published which show them — but they are the exception rather 

 than the rule, and do not invalidate the generalization that the prevailing 

 type of morainic topography is irregular in character. 



To this condition of things the mountains of Kerry form a notable 

 contrast. The moraines, which almost e\erywhere cover the lowlands at tlie 

 foot of the mountains, show a persistent and well-marked linear arrange- 

 ment, and often form unbroken ramparts many miles in length. They are 

 arranged, moreover, in concentric series one within the other, the intervening 

 intervals being free from moraine, or only covered by a thin deposit, nut 

 rising into mounds. I can see nothing in the topography of the Kerry 

 mountains as compared with the Highlands of Scotland which would lead 

 one to ascribe this difierence to local circumstances, and have so come to 

 believe that ihe two types of morainic formation are in some way an 

 expression of different climatic conditions during the retreat of ihe ice. 



The glacial ion of the mountains of Iveragh and Dunkerron was eH'ected 

 in the main by ice from a centre of distribution in the low country west of 

 Kenmare. The demonstration of this need nut be included here. It is 



K.I. A. PROC, VOL. XXXV, SKCT. B. [O] 



