SHARPE ON NORTH WALES. 307 



merate, alternating with beds of grey chert. The bedding dips east. 

 This rock the author refers to the old red sandstone. This con- 

 glomerate is cut off by a second fault, which also runs north-east, 

 and comes out on the shore at a hollow in the cliff near Gared-gith, 

 about a quarter of a mile beyond the former fault. Between the 

 two faults there is a good section of the conglomerate. 



To the east of the second fault, extending along the cliff about a 

 mile, as far as Garth point, and covering the valley of Bangor, lie va- 

 rious brown and liver-coloured shales, referred by the author to the 

 Ludlow series. 



The axis of the hill east of Bangor is a greenstone trap. It runs 

 S.S.E., and has disturbed and twisted about the Ludlow rocks, and 

 has given them a high inclination. They dip between the Straits and 

 Bangor E.S.E. 30°; west of the trap, W.N.W. 60°; east of the trap 

 south-east, at a high angle : further to the east they are lost below 

 the drift already described. 



Since the beds on both sides of the two faults agree in having a 

 dip eastward, if the faults were overlooked the Ludlow beds around 

 Bangor would appear to lie above the magnesian limestone; and it 

 is from that circumstance probably that Mr. Greenough in his Geo- 

 logical Maps has been led to colour these Ludlow shales as new red 

 sandstone. Unless the thickness of the Wenlock series has been 

 greatly reduced in this part of North Wales, it is impossible that it 

 should lie concealed under the deposit of drift which skirts the Snow- 

 don chain. It is by no means improbable however that in this part 

 of Carnarvonshire the Wenlock series is entirely wanting ; that con- 

 sequently the igneous rock which flanks that chain is overlaid by the 

 Ludlow shales ; and therefore that the stratified formation next above 

 the Lower Silurian slates is the Ludlow rock. This cannot be 

 decided owing to the covering of gravel, which completely conceals 

 the stratification. 



At the north-east angle of the county, the Wenlock rocks of Den- 

 bighshire cross the river Conway above Caer-hun, four miles and a 

 half south of Conway, and, forming a band about two miles wide, 

 they pass along the left bank of the river to the north of Conway 

 town. Along this line they abut unconformably against the Lower 

 Silurian and igneous rocks of the Snowdon chain. 



General Remarks on the Upper and Lower Silurian and Cambrian 

 Formations of North Wales, 



The principal points of difference which the author has had occa- 

 sion to observe between the Silurian and Cambrian rocks of North 

 Wales and those of the English border counties, are arranged by him 

 under the three following heads : — 



1st. The greater thickness of each formation in North Wales. 



2nd. The paucity of organic remains in North Wales, and that 

 even in beds which in the English border counties are crowded with 

 fossils. 



3rd. The prevalence of slaty cleavage in North Wales. 



