On the Physical Geoloyy of the Neighbourhood of Dublin. 157 



larger or Lower Lough Bray (elevation 1,225 feet) is clammed in 

 by a glacial moraine, the two arms of which meet at the bottom 

 of the lake and then descend towards the bottom of Glencree 

 valley, near the head of which the lakes are situated. Their 

 lower parts below the lake are covered with numerous large 

 granite blocks, some of which must weigh about 200 tons. That 

 part of the grounds of Lough Bray Cottage which is on the N. 

 side of the lake is on a bank leaning against the hill side ; the 

 upper side of this bank falls to the hill side. The lower eastern 

 end of the bank is beneath the water of the lake. This is clearly 

 a latero- terminal moraine formed by the glacier when it had 

 shrunk so as to be unable to fill the original moraine bed it had 

 made for itself. (The jointing of the highest part of the precipice 

 is well seen from the ground between the two lakes. In the 

 lower part of the precipice the primary jointing dips inwards, 

 and is as regular as stratification ; at the summit it is horizontal.) 

 The small Upper Lough (elevation 1,453 feet) might be con- 

 sidered by some the more interesting, glacially, of the two. 

 It is contained in its own recess which is much less deep 

 than that of the Lower Lake. If we may so express it, 

 the width of the Upper Lake is greater than its length. 

 Its longest axis is parallel to the cliff under which it lies and to 

 the moraine dam. This dam is a well defined bank running all 

 along the lower edge of the lake ; at its middle part it rises about 

 90 feet above the water. It is represented, but without the 

 following small details, on the shaded Ordnance inch map, 121. 

 All along its top runs a small, very distinct, ridge or crest, which 

 looks almost like an artificial bank, and close outside of this, for 

 the S.E. half of its length runs a second parallel but not so 

 regular crest. Several huge blocks of granite are scattered about 

 on this moraine dam ; one lies right on the first mentioned crest. 

 Some of these must be 200 tons in weight ; the largest (on the 

 outer side of the moraine) measures 28 feet in width at its base, 

 26 feet in height, with a mean thickness of about 9 feet ; it must 

 weigh at least 250 tons. These blocks have, no doubt, come 

 from the cliff on the opposite side of the lake. It is interesting 

 to have this evidence of so great power in so small a glacier. No 

 rock- scoring is to be seen; the rocks being all concealed by the 

 moraine masses, except in the precipices over the lakes. 



