118 



Report on the Moel Tvyfaen Drift. 



districts, dark grey in colour and full of stones (Photograpli 4). 

 The stones are for the most part of moderate size, but some up to 

 3^ and 3 feet (the visible part) occur. They are subangular and 

 well striated. There seems to be a general slight upward inclination 

 of the longer axes of the stones to E.S.E. or E. The longer axis of 

 the large boulder mentioned pointed W. 20 S. — E. 20 N., and its 

 eastern end was a little lifted. Nearly all the stones observed were 

 of North Welsh origin, the riebeckite eurite of Mynydd Mawr being 

 very abundant, but one pebble of a granite foreign to North Wales 

 was obtained on November 5 (7, p. 120). Extensive sections will 

 remain, in which all points not depending upon orientation can be 

 observed. 



12. Nature of Junction of Sandy Group and Boulder-clay (Photo- 

 graphs 5, 6). — In a general way the sandy group passes under the 

 Boulder-clay to the E.S.E. , as described by previous writers. 

 The sandy beds in places dip W. at the junction, and are also 

 contorted, a string of loamy sand two inches thick being bent into 

 sharp folds (Fig. 2). These contortions,^ however, were not very 

 clearly displayed on November 5 on account of slipping. 



The Boulder-clay rests upon an uneven surface of the sandy beds, 

 as shown in the annexed section (Fig. 3), which was measured, and 

 is drawn to scale. 



The photograph No. 5 is taken close to the E.S.E. end of this 

 section. The Boulder-clay is " good typical stony till," and the 

 underlying beds the usual sand and yellow loam with gravelly 

 streaks and pockets containing shell fragments. In the lowest 

 layers are angular fragments of slate, below which is broken slate 



Sou/sr^i 



snif 



tnUi I • - ^ - 



Floor of Gallery No. 1. 



Fig. 3. — Junction of Boulder-clay and Sandy Beds. 

 (Scale 1 inch = 36 feet ; length of section 144 ft. 6 in.) 



mixed with a small quantity of clayey matter resting on slate with 

 terminal curvature. 



Evidence has been adduced by previous writers to show that the 

 sandy group overlies as well as underlies the Boulder-clay, so that 

 the two groups interdigitate. The section as seen on November 5 

 could not be said to be conclusive on this point ; but it is shown 



1 Very well seen on September 26. — H. H. 



