TRANSACTIONS OF SECTION C. 691 



2. Note on a few of the many remarkable Boulder-stones to he found along 

 the Eastern Margin of the WicMow Mountains. By Professoi" Edward 

 Hull, LL.B., F.B.S., F.G.S. 



Amongst the evidences of tlie former existence of an extensive sheet of ice 

 descending from the AVicklow Mountains towards the shores of the Irish Sea is the 

 occurrence of boulder-stones, chiefly formed of granite or granitoid gneiss, derived 

 from the mountainous range to the westward, of a size seldom equalled — probably 

 ■not surpassed — amongst the British Isles. As the Association includes in its 

 labours the task of collecting details regarding erratic blocks, it may prove of 

 interest if I record a few cases which have come under my own notice. 



1. The Mottha St<me. — This remarkable boulder is perched on the summit of 

 ■Cronbane Hill, above Castle Howard, and is a conspicuous object from all directions. 

 It consists of grey granite, and rests upon Lower Silurian slate. Its dimensions 

 are nearly as follows : — length, 14 feet ; height, 9 feet ; breadth, 9 feet. It contains 

 about 35 cubic yards of matter, and its weight would be about 70 tons. From the 

 site of the Mottha Stone, at a level of 816 feet above the sea, the eye ranges west- 

 ward along the magniticent valley of Glenmalure, to the flanks of Lugnaquilla, at 

 a distance of about ten or twelve miles, whence, as we may suppose, the granite 

 tlock started on its journey. In its course it must have crossed the deep hollow of 

 the Avonmore valley, which extends just below the feet of the observer transversely 

 to the patli of this remarkable erratic block. 



2. C'adle Kevin. — In the valley between Castle Kevin and Moneystown, where 

 large boulders are numerous, there lies a block of granite, partially imbedded of 

 ■which the dimensions are: — length, 15 feet ; breadth, 10 ieet ; height, 9 feet (im- 

 Ijedded portion — probably 3 feet — is not included in above). This block contains 

 about 50 cubic yards of matter, and is about 100 tons in weight. The birthplace 

 of this boulder was probably the mountainous tract about Mullaghcleevaun, 2,7Sc{ 

 feet in height, lying at tbe head of the valley in which is situated the deep waters 

 of Lough Dan, and it probably travelled a distance of eight or nine miles in an 

 E.S.E. direction. 



3. The last boulder-stone that I shall mention is the largest I have met with in 

 CO. Wicklow — perhaps in ihe British Islands. It stands behind a cottage by the 

 roadside, near Eouudwood Church, and is quite as large as the cottage itself, to 

 ■which it forms a good protection from the storms descending from the mountains 

 behind. This boulder consists of granitoid gneiss, resting ou Lower Silurian slate 

 and grit. Its dimensions are (q. p.") : — length, 21 feet ; breadth, 14 feet ; height, 

 12 feet. Its form is somewhat oval, and it contains about 120 cubic yards of 

 matter, and is about 240 tons in weight. The source of this block, which lies at 

 an elevation of about 800 feet above the sea, was probably in the same locality 

 with that of the Castle Kevin boulder, and the distance travelled was about six or 

 eeven miles. 



The blocks above noticed, with many others of smaller size, do not belong to any 

 of the local glaciers which once filled the valleys towards the close of the glacial 

 epoch, and which have left numerous well-formed moraines in nearly all the prin- 

 cipal valleys descending from the Wicklow range. They are to be referred, in all 

 probability, to the earlier stage of intense glaciation, during which the whole district 

 was covered with perennial snows and ice, moving eastward into the hollow now 

 occupied by the waters of the Irish Sea. 



3. The Terminal Moraines of the Great Glaciers of England. 

 By Professor H. Carvill Lewis. 



The investigation here recorded is based upon the important principle that 

 every glacier at the time of its greatest extension is hounded and limited by a ter- 

 minal moraine. Supposed exceptions to this law in Switzerland and elsewhere had 

 been studied by the author and found to be contrary to observed facts. Thus the 

 ancient Rhone glacier, stated by Swiss geologists to be without a limiting moraine 

 at the time of its greatest extension, was found to have one as distinct as those of 



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