BOFLDER-CLAT OF CHESHIRE. 



597 



moraine mound at Leighton Hall ; and another, of fantastic shape, is 

 hardly distinguishable from an example near Shap, whilst others 

 of a similar kind bear a striking resemblance to each other. 



Fig. 6. — Weathered hlocJc 

 from Moraine. (One 

 third natural size.) 



rig. 7. — Weathered hlock from 

 Moraine. (One third natural 

 size.) 



Several blocks, subsequently to being weathered, have had portions 

 of their surface rubbed ; this generally occurs over a very limited 

 space, and leaves adjoining and even more prominent parts entirely 

 untouched (fig. 5). Ko example has jet been found in moraines; 

 but it may be concluded that this attrition could not have been 

 caused by propulsion along the rock-surface over which the glacier 

 moved. It is more probable that, carried forward by an accumulating 

 glacier, thin pebbles have rubbed against others imbedded in the 

 same moraine-heap. 



Pieces of flint occur in the Boulder-clay, but they are rare. 

 Some have had flakes forcibly broken off", it may be several from 

 the same specimen : occasionally the depression is formed which is 

 the counterpart to the " bulb of percussion ; " and at this point the 

 flint is sometimes crushed as if from the intensity of the pressure 

 by which a flake has been splintered off. In others the more 

 prominent and rounded portions of the nodules bear evidence of 

 being rubbed and chipped as by a grinding motion under pressure. 

 There are none which have been rounded by the rolling motion 

 caused by waves or currents. 



The rarity of flints in the Boulder-clay is not surprising if it is 

 considered that they have been carried into the Bay of Liverpool by 

 means of icebergs and floes which ploughed their way across 

 through closely packed ice, distributing their load of boulders in the 

 passage ; even in the glacial accumulations in the neighbourhood 

 of Belfast, in close proximity to the Chalk formation, they are not 

 found to be very abundant. Many of the flints in the Eskers and 



