_— 
ON THE DRIFT AT MOEL TRYFAEN. 417 
N. Wales was obtained on November 5 (y, p. 419). 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 con- 
tortions,! 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, 
Fic. 3.,—Junction of Boulder Clay and Sandy Beds. 
cS eneaE ana an men i | mM 
ie aT OTH rin | aii il} mu HN | I) 
loor of Gallery No. 1. 
Scale lin. = 36 ft. Length of Section 144 ft. 6 in. 
peace’ 
below which is broken slate 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 in Photograph No. 6, of which fig. 4 
isan explanatory diagram : (a) is very stony boulder clay, stones mainly of 
Welsh origin ; (6) yellow loam and sand bedded and contorted ; (c) bedded 
sand and gravel, 1 ft. to 2 ft.; (d) soil6in. The lower edge of the boulder 
clay dips downward into the exposed face rather steeply. BBB are boulders 
with angular ends projecting from the clay into the sand, the largest being 
apparently of Penmaenmawr diorite, and the other two of riebeckite eurite 
of Mynydd Mawr. There is no distinct evidence that the shelly sand and 
gravel anywhere overlie the boulder clay. A close examination showed a 
distinct line, probably of erosion, between that which passes above and that 
which passes beneath the boulder clay, in which last only were shell frag- 
ments found. The sand and gravel above the boulder clay may be altogether 
? Very well seen on September 26.—H. H. 
1899, EE 
