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ON EXCAVATIONS IN THR PAL®OZOIC ROCKS OF WALES, ETC. 137 
Excavation No. 45, Southwards from the Spring. 
Similar trial-holes were made at intervals upon the surface of the 
slope to the south of the Spring in the direction of another known 
exposure of Bala rock. In each instance the existence of Cambrian shale 
was proved, with here and there ill-defined examples of, probably, the 
same Orthis, but no fossiliferous band was observed. The shale retained 
its general characteristics, but was so much crushed that dip and strike 
could not be satisfactorily. determined within the limits of the shallow 
excavations. A nearer approximation to the line between the Cambrian 
and the Bala at this point can now be laid down on the map, but the 
actual contact was obscured by the presence of many large blocks of 
sandstone belonging to the younger series. If, as seems probable, the 
Cambrian shales retain the north and south strike observed near the 
Spring for a considerable distance, the Bala beds are strongly dis- 
cordant to them, with a south-east and north-west trend. 
(B) Excavations ALONG CoMLEY Brook. 
The prolonged drought of the summer of 1911 provided an excellent 
epportunity for examining the beds of shale and sandstone which were 
known to occur in the bed of the Brook as well as in the slope above its 
left bank, and I was able to make considerable additions to our knowledge 
of the inter-relations of the various rocks and of their fossil contents. 
The rocks composing the little elevation called Dairy Hill were 
proved in my first and second reports (Dublin 1908, and Winnipeg 1909) 
to be folded into a dome, consisting of a core of Lower Comley Sandstone 
(Lower Cambrian-Oienellus zones) with a covering of the Quarry Ridge 
Grits (Middle Cambrian-Paradoxides zones). The Comley Brook has 
cut into the western flank of this dome, and affords some poor natural 
exposures of its component rocks which are much obscured by vegeta- 
tion. The excavation work consisted principally of clearing away soil 
and herbage wherever rock was visible, with occasional pickaxe work in 
the rock itself. 
A straight line of fence (seen near the numbers representing Excava- 
tions Nos. 12 and 13 on the map published with the Sheffield Repor‘) 
forms the south-east boundary of the enclosure called Dairy Hill, and 
cuts the line of the Brook at right angles. This forms a convenient 
point from which measurements may be taken. The exposures in the 
hed of the Brook down-stream (north-west of this point) are described 
below as Excavation No. 46, and those up-stream (south-east) as Excava- 
tion No, 47. 
Ezcavation No, 46, Comley Brook. 
Opposite the fence above mentioned, brownish shale with bands of 
hard ringing grit, agreeing in character, strike, and dip with those of 
Excavation No. 13 (Dublin Report, 1908) are to be seen in the Brook. 
At 18 yards to the north-west there is a mass of blue-grey, much 
fractured shale, weathering brown ; at 36 yards similar shale with a strong 
westerly dip occurs, and has yielded a few small fossils, among which 
